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</style></head><body><div class="book"><div class="titlepage"><div><div><h1 class="title"><a id="xtrans"></a>X Transport Interface</h1></div><div><h2 class="subtitle">X Consortium Standard</h2></div><div><div class="authorgroup"><div class="author"><h3 class="author"><span class="firstname">Stuart</span> <span class="surname">Anderson</span></h3><div class="affiliation"><span class="orgname">NCR Corporation<br /></span></div></div><div class="othercredit"><h3 class="othercredit"><span class="firstname">Ralph</span> <span class="surname">Mor</span></h3><div class="affiliation"><span class="orgname">X Consortium<br /></span></div></div><div class="othercredit"><h3 class="othercredit"><span class="firstname">Alan</span> <span class="surname">Coopersmith</span></h3><div class="affiliation"><span class="orgname">Oracle Corp.<br /></span></div></div></div></div><div><p class="releaseinfo">X Version 11, Release 7.7</p></div><div><p class="releaseinfo">Version 1.2</p></div><div><p class="copyright">Copyright © 1993, 1994 NCR Corporation - Dayton, Ohio, USA</p></div><div><div class="legalnotice"><a id="idm27"></a><p>
All Rights Reserved
</p><p>
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation, and that the name NCR not be used in advertising
or publicity pertaining to distribution of the software without specific,
written prior permission.  NCR makes no representations about the
suitability of this software for any purpose.  It is provided "as is"
without express or implied warranty.
</p><p>
NCR DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
NO EVENT SHALL NCR BE LIABLE FOR ANY SPECIAL, INDIRECT OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
</p></div></div><div><div class="legalnotice"><a id="idm31"></a><p class="multiLicensing">
Copyright © 1993, 1994, 2002 The Open Group
</p><p>
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
</p><p>
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
</p><p>
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
</p><p>
Except as contained in this notice, the name of The Open Group shall not be
used in advertising or otherwise to promote the sale, use or other dealings
in this Software without prior written authorization from The Open Group.
</p><p>
X Window System is a trademark of The Open Group, Inc.
</p></div></div></div><hr /></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="preface"><a href="#idm38">The X Transport Interface</a></span></dt><dt><span class="chapter"><a href="#Purposes_and_Goals">1. Purposes and Goals</a></span></dt><dt><span class="chapter"><a href="#Overview_of_the_Interface">2. Overview of the Interface</a></span></dt><dt><span class="chapter"><a href="#Definition_of_Address_Specification_Format">3. Definition of Address Specification Format</a></span></dt><dt><span class="chapter"><a href="#Internal_Data_Structures">4. Internal Data Structures</a></span></dt><dd><dl><dt><span class="sect1"><a href="#Xtransport">Xtransport</a></span></dt><dt><span class="sect1"><a href="#XtransConnInfo">XtransConnInfo</a></span></dt></dl></dd><dt><span class="chapter"><a href="#Exposed_Transport_Independent_API">5. Exposed Transport Independent API</a></span></dt><dd><dl><dt><span class="sect1"><a href="#Core_Interface_API">Core Interface API</a></span></dt><dt><span class="sect1"><a href="#Utility_API">Utility API</a></span></dt></dl></dd><dt><span class="chapter"><a href="#Transport_Option_Definition">6. Transport Option Definition</a></span></dt><dt><span class="chapter"><a href="#Hidden_Transport_Dependent_API">7. Hidden Transport Dependent API</a></span></dt><dt><span class="chapter"><a href="#Configuration">8. Configuration</a></span></dt><dt><span class="chapter"><a href="#Transport_Specific_Definitions">9. Transport Specific Definitions</a></span></dt><dt><span class="chapter"><a href="#Implementation_Notes">10. Implementation Notes</a></span></dt></dl></div><div class="preface"><div class="titlepage"><div><div><h1 class="title"><a id="idm38"></a>The X Transport Interface</h1></div></div></div><p>
Designed by Stuart Anderson (NCR) with help from Ralph Mor (X Consortium)
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
This documentation does not completely match the implementation in R6
(as a result of some late changes made in the code). Specifically, support
was added for font server cloning, and conditional compliation was introduced
for client vs. server code.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Purposes_and_Goals"></a>Chapter 1. Purposes and Goals</h1></div></div></div><p>The X Transport Interface is intended to combine all system and
transport specific code into a single place in the source tree. This API
should be used by all libraries, clients and servers of the X Window System.
Use of this API should allow the addition of new types of transports and
support for new platforms without making any changes to the source except
in the X Transport Interface code.</p><p>This interface should solve the problem of multiple
<code class="code">#ifdef TRANSPORT</code> and <code class="code">#ifdef PLATFORM</code>
statements scattered throughout the source tree.</p><p>This interface should provide enough functionality to support all
types of protocols, including connection oriented protocols such as X11 and
FS, and connection-less oriented protocols such as XDMCP.</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Overview_of_the_Interface"></a>Chapter 2. Overview of the Interface</h1></div></div></div><p>
The interface provides an API for use by applications. The functions in
this API perform work that is common to all transports and systems, such
as parsing an address into a host and port number. The functions in this
API call transport specific functions that are contained in a table whose
contents are defined at compile time. This table contains an entry for each
type of transport. Each entry is a record containing mostly pointers to
function that implements the interface for the given transport.
</p><p>
This API does not provide an abstraction for <code class="function">select()</code>
or <code class="function">poll()</code>.
These functions are themselves transport independent, so an additional
interface is not needed for these functions. It is also unclear how such
an interface would affect performance.
</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Definition_of_Address_Specification_Format"></a>Chapter 3. Definition of Address Specification Format</h1></div></div></div><p>
Addresses are specified in the following syntax,

</p><pre class="synopsis">
<em class="replaceable"><code>protocol</code></em>/<em class="replaceable"><code>host</code></em>:<em class="replaceable"><code>port</code></em>
</pre><p>

where <em class="replaceable"><code>protocol</code></em> specifies a protocol family
or an alias for a protocol family. A definition of common protocol
families is given in a later section.
</p><p>
The <em class="replaceable"><code>host</code></em> part specifies the name of a host or other
transport dependent entity that could be interpreted as a Network Service Access Point
(NSAP).
</p><p>
The <em class="replaceable"><code>port</code></em> part specifies the name of a Transport Service
Access Point (TSAP). The format of the TSAP is defined by the underlying transport
implementation, but it is represented using a string format when it is
part of an address.
</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Internal_Data_Structures"></a>Chapter 4. Internal Data Structures</h1></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="#Xtransport">Xtransport</a></span></dt><dt><span class="sect1"><a href="#XtransConnInfo">XtransConnInfo</a></span></dt></dl></div><p>
There are two major data structures associated with the transport
independent portion of this interface.  Additional data structures
may be used internally by each transport.
</p><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Xtransport"></a>Xtransport</h2></div></div></div><p>
Each transport supported has an entry in the transport table. The transport
table is an array of Xtransport records. Each record contains all the entry
points for a single transport. This record is defined as:
</p><pre class="synopsis">
typedef struct _Xtransport {

    const char *TransName;
    int  flags;

    XtransConnInfo (*OpenCOTSClient)(
     struct _Xtransport *,    /* transport */
     const char *,            /* protocol */
     const char *,            /* host */
     const char *             /* port */
    );

    XtransConnInfo (*OpenCOTSServer)(
     struct _Xtransport *,    /* transport */
     const char *,            /* protocol */
     const char *,            /* host */
     const char *             /* port */
    );

    int     (*SetOption)(
     XtransConnInfo,          /* connection */
     int,               /* option */
     int               /* arg */
    );

    int     (*CreateListener)(
     XtransConnInfo,          /* connection */
     const char *,            /* port */
     int                      /* flags */
    );

    int     (*ResetListener)(
     XtransConnInfo          /* connection */
    );

    XtransConnInfo (*Accept)(
     XtransConnInfo          /* connection */
    );

    int     (*Connect)(
     XtransConnInfo,          /* connection */
     const char *,            /* host */
     const char *             /* port */
    );

    int     (*BytesReadable)(
     XtransConnInfo,          /* connection */
     BytesReadable_t *     /* pend */
    );

    int     (*Read)(
     XtransConnInfo,          /* connection */
     char *,               /* buf */
     int               /* size */
    );

    int     (*Write)(
     XtransConnInfo,          /* connection */
     char *,               /* buf */
     int               /* size */
    );

    int     (*Readv)(
     XtransConnInfo,          /* connection */
     struct iovec *,          /* buf */
     int               /* size */
    );

    int     (*Writev)(
     XtransConnInfo,          /* connection */
     struct iovec *,          /* buf */
     int               /* size */
    );

    int     (*Disconnect)(
     XtransConnInfo          /* connection */
    );

    int     (*Close)(
     XtransConnInfo          /* connection */
    );

} Xtransport;
</pre><p>
The <em class="structfield"><code>flags</code></em> field can contain an OR of
the following masks:
</p><div class="variablelist"><table border="0" class="variablelist"><colgroup><col align="left" valign="top" /><col /></colgroup><tbody><tr><td><p><span class="term"><span class="symbol">TRANS_ALIAS</span></span></p></td><td><p>
indicates that this record is providing an alias, and should
not be used to create a listener.
      </p></td></tr><tr><td><p><span class="term"><span class="symbol">TRANS_LOCAL</span></span></p></td><td><p>
indicates that this is a <span class="symbol">LOCALCONN</span> transport.
    </p></td></tr><tr><td><p><span class="term"><span class="symbol">TRANS_ABSTRACT</span></span></p></td><td><p>
indicates that a local connection transport uses the abstract socket namespace.
    </p></td></tr></tbody></table></div><p>
</p><p>
Some additional flags may be set in the <em class="structfield"><code>flags</code></em>
field by the library while it is running:
</p><div class="variablelist"><table border="0" class="variablelist"><colgroup><col align="left" valign="top" /><col /></colgroup><tbody><tr><td><p><span class="term"><span class="symbol">TRANS_DISABLED</span></span></p></td><td><p>
indicates that this transport has been disabled.
    </p></td></tr><tr><td><p><span class="term"><span class="symbol">TRANS_NOLISTEN</span></span></p></td><td><p>
indicates that servers should not open new listeners using this transport.
    </p></td></tr><tr><td><p><span class="term"><span class="symbol">TRANS_NOUNLINK</span></span></p></td><td><p>
set by a transport backend to indicate that the endpoints for its connection
should not be unlinked.
    </p></td></tr></tbody></table></div><p>
</p></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="XtransConnInfo"></a>XtransConnInfo</h2></div></div></div><p>
Each connection will have an opaque <span class="structname">XtransConnInfo</span>
transport connection
object allocated for it. This record contains information specific to the
connection. The record is defined as:

</p><pre class="synopsis">
typedef struct _XtransConnInfo *XtransConnInfo;

struct _XtransConnInfo {
    struct _Xtransport     *transptr;
    char     *priv;
    int          flags;
    int          fd;
    int          family;
    char     *addr;
    int          addrlen;
    char     *peeraddr;
    int          peeraddrlen;
};
</pre><p>
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Exposed_Transport_Independent_API"></a>Chapter 5. Exposed Transport Independent API</h1></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="#Core_Interface_API">Core Interface API</a></span></dt><dt><span class="sect1"><a href="#Utility_API">Utility API</a></span></dt></dl></div><p>
This API is included in each library and server that uses it. The API may
be used by the library, but it is not added to the public API for that
library. This interface is simply an implementation facilitator. This API
contains a low level set of core primitives, and a few utility functions
that are built on top of the primitives.  The utility functions exist to
provide a more familiar interface that can be used to port existing code.
</p><p>
A macro is defined in Xtrans.h for TRANS(func) that creates a unique function
name depending on where the code is compiled. For example, when built for
Xlib, <code class="function">TRANS(OpenCOTSClient)</code> becomes
<code class="function">_X11TransOpenCOTSClient</code>.
</p><p>
All failures are considered fatal, and the connection should be closed
and re-established if desired. In most cases, however, the value of
errno will be available for debugging purposes.
</p><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Core_Interface_API"></a>Core Interface API</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: bullet; "><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSOpenCOTSClient"></a><p><code class="funcdef">XtransConnInfo <strong class="fsfunc">TRANS(OpenCOTSClient)</strong>(</code>const char *<var class="pdparam">address</var><code>)</code>;</p></div><p>
This function creates a Connection-Oriented Transport that is
suitable for use by a client. The parameter <em class="parameter"><code>address</code></em>
contains the full address of the server to which this endpoint will be
connected.  This function returns an opaque transport connection object on
success, or <code class="constant">NULL</code> on failure.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSOpenCOTSServer"></a><p><code class="funcdef">XtransConnInfo <strong class="fsfunc">TRANS(OpenCOTSServer)</strong>(</code>const char *<var class="pdparam">address</var><code>)</code>;</p></div><p>
This function creates a Connection-Oriented Transport that is suitable
for use by a server. The parameter <em class="parameter"><code>address</code></em> contains the
full address to which this server will be bound. This function returns an
opaque transport connection object on success, or <code class="constant">NULL</code>
on failure.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSSetOption"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(SetOption)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, int <var class="pdparam">option</var>, int <var class="pdparam">arg</var><code>)</code>;</p></div><p>
This function sets transport options, similar to the way
<code class="function">setsockopt()</code> and <code class="function">ioctl()</code> work.
The parameter <em class="parameter"><code>connection</code></em> is an endpoint
that was obtained from <code class="function">_XTransOpen*()</code> functions.
The parameter <em class="parameter"><code>option</code></em> contains the option that will
be set. The actual values for <em class="parameter"><code>option</code></em> are defined in a
<a class="link" href="#Transport_Option_Definition" title="Chapter 6. Transport Option Definition">later section</a>.
The parameter <em class="parameter"><code>arg</code></em> can be used to pass
in an additional value that may be required by some options.
This function returns 0 on success and -1 on failure.
    </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
Based on current usage, the complimentary function
<code class="function">TRANS(GetOption)</code> is not necessary.
    </p></div></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSCreateListener"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(CreateListener)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, const char *<var class="pdparam">port</var>, int <var class="pdparam">flags</var><code>)</code>;</p></div><p>
This function sets up the server endpoint for listening. The parameter
<em class="parameter"><code>connection</code></em> is an endpoint that was obtained from
<code class="function">TRANS(OpenCOTSServer)()</code>. The parameter
<em class="parameter"><code>port</code></em> specifies the port to which this endpoint
should be bound for listening. If port is <code class="constant">NULL</code>,
then the transport may attempt to allocate any available TSAP for this
connection. If the transport cannot support this, then this function will
return a failure. The <em class="parameter"><code>flags</code></em> parameter can be set
to <span class="symbol">ADDR_IN_USE_ALLOWED</span> to allow the call to the underlying
binding function to fail with a <span class="errorname">EADDRINUSE</span> error
without causing the <code class="function">TRANS(CreateListener)</code>
function itself to fail. This function return 0 on success and -1 on failure.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSResetListener"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(ResetListener)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var><code>)</code>;</p></div><p>
When a server is restarted, certain listen ports may need to be reset.
For example, unix domain needs to check that the file used for
communication has not been deleted. If it has, it must be recreated.
The parameter <em class="parameter"><code>connection</code></em> is an opened and bound
endpoint that was obtained from <code class="function">TRANS(OpenCOTSServer)()</code>
and passed to <code class="function">TRANS(CreateListener)()</code>.
This function will return one of the following values:
<span class="symbol">TRANS_RESET_NOOP</span>,
<span class="symbol">TRANS_RESET_NEW_FD</span>, or
<span class="symbol">TRANS_RESET_FAILURE</span>.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSAccept"></a><p><code class="funcdef">XtransConnInfo <strong class="fsfunc">TRANS(Accept)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var><code>)</code>;</p></div><p>
Once a connection indication is received, this function can be called to
accept the connection. The parameter <em class="parameter"><code>connection</code></em> is
an opened and bound endpoint that was obtained from
<code class="function">TRANS(OpenCOTSServer)()</code> and passed to
<code class="function">TRANS(CreateListener)()</code>. This function will return a
new opaque transport connection object upon success,
<code class="constant">NULL</code> otherwise.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSConnect"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(Connect)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, const char *<var class="pdparam">address</var><code>)</code>;</p></div><p>
This function creates a connection to a server. The parameter
<em class="parameter"><code>connection</code></em> is an endpoint that was obtained
from <code class="function">TRANS(OpenCOTSClient)()</code>. The parameter
<em class="parameter"><code>address</code></em> specifies the TSAP to which this endpoint
should connect. If the protocol is included in the address, it will be
ignored. This function returns 0 on success and -1 on failure.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSBytesReadable"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(BytesReadable)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, BytesReadable_t *<var class="pdparam">pend</var><code>)</code>;</p></div><p>
This function provides the same functionality as the
<code class="function">BytesReadable</code> macro.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSRead"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(Read)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, char *<var class="pdparam">buf</var>, int <var class="pdparam">size</var><code>)</code>;</p></div><p>
This function will return the number of bytes requested on a COTS
connection, and will return the minimum of the number bytes requested.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSWrite"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(Write)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, char *<var class="pdparam">buf</var>, int <var class="pdparam">size</var><code>)</code>;</p></div><p>
This function will write the requested number of bytes on a COTS
connection.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSReadv"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(Readv)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, struct iovec *<var class="pdparam">buf</var>, int <var class="pdparam">size</var><code>)</code>;</p></div><p>
Similar to <code class="function">TRANS(Read)()</code>.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSWritev"></a><p><code class="funcdef">  int <strong class="fsfunc">TRANS(Writev)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, struct iovec *<var class="pdparam">buf</var>, int <var class="pdparam">size</var><code>)</code>;</p></div><p>
Similar to <code class="function">TRANS(Write)()</code>.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSDisconnect"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(Disconnect)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var><code>)</code>;</p></div><p>
This function is used when an orderly disconnect is desired. This function
breaks the connection on the transport. It is similar to the socket function
<code class="function">shutdown()</code>.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSClose"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(Close)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var><code>)</code>;</p></div><p>
This function closes the transport, unbinds it, and frees all resources that
was associated with the transport. If a <code class="function">TRANS(Disconnect)</code>
call was not made on the connection, a disorderly disconnect may occur.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSIsLocal"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(IsLocal)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var><code>)</code>;</p></div><p>
Returns TRUE if it is a local transport.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSGetMyAddr"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(GetMyAddr)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, int *<var class="pdparam">familyp</var>, int *<var class="pdparam">addrlenp</var>, Xtransaddr **<var class="pdparam">addrp</var><code>)</code>;</p></div><p>
This function is similar to <code class="function">getsockname()</code>.
This function will allocate space for the address, so it must be freed by
the caller. Not all transports will have a valid address until a connection
is established.  This function should not be used until the connection is
established with <code class="function">Connect()</code> or
<code class="function">Accept()</code>.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSGetPeerAddr"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(GetPeerAddr)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var>, int *<var class="pdparam">familyp</var>, int *<var class="pdparam">addrlenp</var>, Xtransaddr **<var class="pdparam">addrp</var><code>)</code>;</p></div><p>
This function is similar to <code class="function">getpeername()</code>.
This function will allocate space for the address, so it must be freed by
the caller. Not all transports will have a valid address until a connection
is established.  This function should not be used until the connection is
established with <code class="function">Connect()</code> or
<code class="function">Accept()</code>.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSGetConnectionNumber"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(GetConnectionNumber)</strong>(</code>XtransConnInfo <var class="pdparam">connection</var><code>)</code>;</p></div><p>
Returns the file descriptor associated with this transport.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSMakeAllCOTSServerListeners"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(MakeAllCOTSServerListeners)</strong>(</code>const char *<var class="pdparam">port</var>, int *<var class="pdparam">partial_ret</var>, int *<var class="pdparam">count_ret</var>, XtransConnInfo **<var class="pdparam">connections_ret</var><code>)</code>;</p></div><p>
This function should be used by most servers. It will try to establish
a COTS server endpoint for each transport listed in the transport table.
<em class="parameter"><code>partial_ret</code></em> will be set to <span class="symbol">True</span> if
only a partial network could be created. <em class="parameter"><code>count_ret</code></em> is
the number of transports returned, and <em class="parameter"><code>connections_ret</code></em>
is the list of transports.
    </p></li></ul></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Utility_API"></a>Utility API</h2></div></div></div><p>
This section describes a few useful functions that have been implemented on
top of the Core Interface API.  These functions are being provided as a
convenience.
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: bullet; "><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="TRANSConvertAddress"></a><p><code class="funcdef">int <strong class="fsfunc">TRANS(ConvertAddress)</strong>(</code>int *<var class="pdparam">familyp</var>, int *<var class="pdparam">addrlenp</var>, Xtransaddr *<var class="pdparam">addrp</var><code>)</code>;</p></div><p>
This function converts a sockaddr based address to an X authorization based
address (ie <span class="symbol">AF_INET</span>, <span class="symbol">AF_UNIX</span> to the X
protocol definition (ie <span class="symbol">FamilyInternet</span>,
<span class="symbol">FamilyLocal</span>)).
    </p></li></ul></div></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Transport_Option_Definition"></a>Chapter 6. Transport Option Definition</h1></div></div></div><p>
The following options are defined for the
<a class="link" href="#TRANSSetOption"><code class="function">TRANS(SetOption)()</code></a>
function. If an OS or transport does not support any of these options,
then it will silently ignore the option.
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: bullet; "><li class="listitem" style="list-style-type: disc"><p>
<span class="symbol">TRANS_NONBLOCKING</span>
    </p><p>
This option controls the blocking mode of the connection. If the argument
is set to 1, then the connection will be set to blocking. If the argument
is set to 0, then the connection will be set to non- blocking.
    </p></li><li class="listitem" style="list-style-type: disc"><p>
<span class="symbol">TRANS_CLOSEONEXEC</span>
    </p><p>
This option determines what will happen to the connection when an exec is
encountered. If the argument is set to 1, then the connection will be
closed when an exec occurs. If the argument is set to 0, then the
connection will not be closed when an exec occurs.
    </p></li></ul></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Hidden_Transport_Dependent_API"></a>Chapter 7. Hidden Transport Dependent API</h1></div></div></div><p>
The hidden transport dependent functions are placed in the Xtransport record.
These function are similar to the Exposed Transport Independent API, but
some of the parameters and return values are slightly different.  Stuff like
the <code class="code">#ifdef SUNSYSV</code> should be handled inside these functions.
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: bullet; "><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="OpenCOTSClient"></a><p><code class="funcdef">XtransConnInfo *<strong class="fsfunc">OpenCOTSClient</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, const char *<var class="pdparam">protocol</var>, const char *<var class="pdparam">host</var>, const char *<var class="pdparam">port</var><code>)</code>;</p></div><p>
This function creates a Connection-Oriented Transport. The parameter
<em class="parameter"><code>thistrans</code></em> points to an Xtransport entry in the
transport table. The parameters <em class="parameter"><code>protocol</code></em>,
<em class="parameter"><code>host</code></em>, and <em class="parameter"><code>port</code></em>, point to
strings containing the corresponding parts of the address that was passed into
<a class="link" href="#TRANSOpenCOTSClient"><code class="function">TRANS(OpenCOTSClient)()</code></a>.
This function must allocate and initialize the contents of the XtransConnInfo
structure that is returned by this function. This function will open the
transport, and bind it into the transport namespace if applicable. The local
address portion of the XtransConnInfo structure will also be filled in by
this function.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="OpenCOTSServer"></a><p><code class="funcdef">XtransConnInfo *<strong class="fsfunc">OpenCOTSServer</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, const char *<var class="pdparam">protocol</var>, const char *<var class="pdparam">host</var>, const char *<var class="pdparam">port</var><code>)</code>;</p></div><p>
This function creates a Connection-Oriented Transport. The parameter
<em class="parameter"><code>thistrans</code></em> points to an Xtransport entry in the
transport table. The parameters <em class="parameter"><code>protocol</code></em>,
<em class="parameter"><code>host</code></em>, and <em class="parameter"><code>port</code></em> point to
strings containing the corresponding parts of the address that was passed into
<a class="link" href="#TRANSOpenCOTSServer"><code class="function">TRANS(OpenCOTSServer)()</code></a>.
This function must allocate and initialize the contents of the
XtransConnInfo structure that is returned by this function. This function
will open the transport.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="SetOption"></a><p><code class="funcdef">int <strong class="fsfunc">SetOption</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, int <var class="pdparam">option</var>, int <var class="pdparam">arg</var><code>)</code>;</p></div><p>
This function provides a transport dependent way of implementing the
options defined by the X Transport Interface. In the current prototype,
this function is not being used, because all of the options defined so far
are transport independent. This function will have to be used if a radically
different transport type is added, or a transport dependent option is defined.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="CreateListener"></a><p><code class="funcdef">int <strong class="fsfunc">CreateListener</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, const char <var class="pdparam">*port</var>, int <var class="pdparam">flags</var><code>)</code>;</p></div><p>
This function takes a transport endpoint opened for a server, and sets it
up to listen for incoming connection requests. The parameter
<em class="parameter"><code>port</code></em>
contains the port portion of the address that was passed to the Open function.
The parameter <em class="parameter"><code>flags</code></em> should be set to
<span class="symbol">ADDR_IN_USE_ALLOWED</span> if the underlying transport endpoint
may be already bound and this should not be considered
as an error. Otherwise flags should be set to 0. This is used by IPv6 code,
where the same socket can be bound to both an IPv6 address and then to a
IPv4 address.  This function will bind the transport into the transport
name space if applicable, and fill in the local address portion of the
XtransConnInfo structure. The transport endpoint will then be set to
listen for incoming connection requests.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="ResetListener"></a><p><code class="funcdef">int <strong class="fsfunc">ResetListener</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var><code>)</code>;</p></div><p>
This function resets the transport for listening.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="Accept"></a><p><code class="funcdef"> XtransConnInfo <strong class="fsfunc">Accept</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var><code>)</code>;</p></div><p>
This function creates a new transport endpoint as a result of an
incoming connection request. The parameter
<em class="parameter"><code>thistrans</code></em> is the endpoint
that was opened for listening by the server. The new endpoint is
opened and bound into the transport’s namespace. A XtransConnInfo
structure describing the new endpoint is returned from this function
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="Connect"></a><p><code class="funcdef">int <strong class="fsfunc">Connect</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, const char *<var class="pdparam">host</var>, const char *<var class="pdparam">port</var><code>)</code>;</p></div><p>
This function establishes a connection to a server. The parameters
<em class="parameter"><code>host</code></em> and <em class="parameter"><code>port</code></em>
describe the server to which the connection should be
established. The connection will be established so that
<code class="function">Read()</code> and
<code class="function">Write()</code> call can be made.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="BytesReadable"></a><p><code class="funcdef">int <strong class="fsfunc">BytesReadable</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, BytesReadable_t *<var class="pdparam">pend</var><code>)</code>;</p></div><p>
This function replaces the <code class="function">BytesReadable()</code>
macro. This allows each transport to have its own mechanism for determining
how much data is ready to be read.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="Read"></a><p><code class="funcdef">int <strong class="fsfunc">Read</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, char *<var class="pdparam">buf</var>, int <var class="pdparam">size</var><code>)</code>;</p></div><p>
This function reads <em class="parameter"><code>size</code></em> bytes into
<em class="parameter"><code>buf</code></em> from the connection.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="Write"></a><p><code class="funcdef">int <strong class="fsfunc">Write</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, char *<var class="pdparam">buf</var>, int <var class="pdparam">size</var><code>)</code>;</p></div><p>
This function writes <em class="parameter"><code>size</code></em> bytes from
<em class="parameter"><code>buf</code></em> to the connection.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="Readv"></a><p><code class="funcdef">int <strong class="fsfunc">Readv</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, struct iovec *<var class="pdparam">buf</var>, int <var class="pdparam">size</var><code>)</code>;</p></div><p>
This function performs a <code class="function">readv()</code> on the connection.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="Writev"></a><p><code class="funcdef">int <strong class="fsfunc">Writev</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var>, struct iovec *<var class="pdparam">buf</var>, int <var class="pdparam">size</var><code>)</code>;</p></div><p>
This function performs a <code class="function">writev()</code> on the connection.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="Disconnect"></a><p><code class="funcdef">int <strong class="fsfunc">Disconnect</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var><code>)</code>;</p></div><p>
This function initiates an orderly shutdown of a connection. If a
transport does not distinguish between orderly and disorderly
disconnects, then a call to this function will have no affect.
    </p></li><li class="listitem" style="list-style-type: disc"><div class="funcsynopsis"><a id="Close"></a><p><code class="funcdef">int <strong class="fsfunc">Close</strong>(</code>struct _Xtransport *<var class="pdparam">thistrans</var><code>)</code>;</p></div><p>
This function will break the connection, and close the endpoint.
    </p></li></ul></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Configuration"></a>Chapter 8. Configuration</h1></div></div></div><p>
The implementation of each transport can be platform specific. It is expected
that existing connection types such as <span class="symbol">TCPCONN</span>,
<span class="symbol">UNIXCONN</span>, <span class="symbol">LOCALCONN</span>, and
<span class="symbol">STREAMSCONN</span> will be replaced with flags for each
possible transport type.
</p><p>
In X11R6, the below flags to enable transport types were set in
<span class="symbol">ConnectionFlags</span> in the <code class="filename">vendor.cf</code> or
<code class="filename">site.def</code> config files.
</p><p>
In X11R7 modular releases, these flags are set when running
<code class="filename">configure</code> scripts which include the
<code class="function">XTRANS_CONNECTION_FLAGS</code> macro from
<code class="filename">xtrans.m4</code>.
</p><div class="informaltable"><table class="informaltable" border="1"><colgroup><col align="left" class="define" /><col align="left" class="enable" /><col align="left" class="desc" /></colgroup><thead><tr><th align="left"><code class="code">#define</code></th><th align="left">configure flag</th><th align="left">Description</th></tr></thead><tbody><tr><td align="left"><span class="symbol">TCPCONN</span></td><td align="left"><code class="option">--enable-tcp-transport</code></td><td align="left">
	Enables the INET (IPv4) Domain Socket based transport
	</td></tr><tr><td align="left"><span class="symbol">IPv6</span></td><td align="left"><code class="option">--enable-ipv6</code></td><td align="left">
	Extends <span class="symbol">TCPCONN</span> to enable IPv6 Socket based transport
	</td></tr><tr><td align="left"><span class="symbol">UNIXCONN</span></td><td align="left"><code class="option">--enable-unix-transport</code></td><td align="left">
	Enables the UNIX Domain Socket based transport
	</td></tr><tr><td align="left"><span class="symbol">STREAMSCONN</span></td><td align="left"><span class="emphasis"><em>Not available in X11R7</em></span></td><td align="left">
	Enables the TLI based transports
	</td></tr><tr><td align="left"><span class="symbol">LOCALCONN</span></td><td align="left"><code class="option">--enable-local-transport</code></td><td align="left">
	Enables the SYSV Local connection transports
	</td></tr><tr><td align="left"><span class="symbol">DNETCONN</span></td><td align="left"><span class="emphasis"><em>Not available in X11R7</em></span></td><td align="left">
	Enables the DECnet transports
	</td></tr></tbody></table></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Transport_Specific_Definitions"></a>Chapter 9. Transport Specific Definitions</h1></div></div></div><div class="informaltable"><table class="informaltable" border="1"><colgroup><col align="center" class="c1" /><col align="center" class="c2" /><col align="center" class="c3" /><col align="center" class="c4" /></colgroup><thead><tr><th rowspan="2" align="center">Protocol Family</th><th colspan="3" align="center">Address Component</th></tr><tr><th align="center">protocol</th><th align="center">host</th><th align="center">port</th></tr></thead><tbody><tr><td align="center">Internet</td><td align="center">inet inet6 tcp udp</td><td align="center">name of an internet addressable host</td><td align="center">string containing the name of a service or a valid port number.  Example: "xserver0", "7100"</td></tr><tr><td align="center">DECnet</td><td align="center">decnet</td><td align="center">name of a DECnet addressable host</td><td align="center">string containing the complete name of the object.  Example: "X$X0"</td></tr><tr><td align="center">NETware</td><td align="center">ipx</td><td align="center">name of a NETware addressable host</td><td align="center">Not sure of the specifics yet.</td></tr><tr><td align="center">OSI</td><td align="center">osi</td><td align="center">name of an OSI adressable host.</td><td align="center">Not sure of the specifics yet.</td></tr><tr><td align="center">Local</td><td align="center">local pts named sco isc</td><td align="center">(ignored)</td><td align="center">String containing the port name, ie "xserver0", "fontserver0".</td></tr></tbody></table></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="Implementation_Notes"></a>Chapter 10. Implementation Notes</h1></div></div></div><p>
This section refers to the prototype implementation that is being developed
concurrently with this document. This prototype has been able to flush out many
details and problems as the specification was being developed.
</p><p>
In X11R6, all of the source code for this interface was located in
<code class="filename">xc/lib/xtrans</code>.
</p><p>
In X11R7, all of the source code for this interface is delivered via
the <code class="systemitem">lib/libxtrans</code> modular package from X.Org,
and is installed under
<code class="filename"><em class="replaceable"><code>${prefix}</code></em>/X11/Xtrans</code>
so that other modules may find it when they build.
</p><p>
All functions names in the source are of the format
<code class="function">TRANS(func)()</code>. The
<code class="function">TRANS()</code>
macro is defined as
</p><pre class="programlisting">
#define TRANS(func) _PROTOCOLTrans##func
</pre><p>
</p><p>
<span class="symbol">PROTOCOL</span> will be uniquely defined in each directory
where this code is compiled.
<span class="symbol">PROTOCOL</span> will be defined to be the name of the protocol
that is implemented by the library or server, such as X11, FS, and ICE.
</p><p>
All libraries and servers that use the X Transport Interface should have a new
file called <code class="filename"><em class="replaceable"><code>TRANSPORT</code></em>trans.c</code>.
This file will include the transports based on the configuration flags
provided by the <code class="filename">configure</code> script. Below is an
example <code class="filename">xfstrans.c</code> for the font server.
</p><pre class="programlisting">
#include "config.h"

#define FONT_t 1
#define TRANS_REOPEN 1
#define TRANS_SERVER 1

#include &lt;X11/Xtrans/transport.c&gt;
</pre><p>
The source files for this interface are listed below.
</p><div class="variablelist"><table border="0" class="variablelist"><colgroup><col align="left" valign="top" /><col /></colgroup><tbody><tr><td><p><span class="term"><code class="filename">Xtrans.h</code></span></p></td><td><p>
Function prototypes and defines for the Transport Independent API.
    </p></td></tr><tr><td><p><span class="term"><code class="filename">Xtransint.h</code></span></p></td><td><p>
Used by the interface implementation only.
Contains the internal data structures.
    </p></td></tr><tr><td><p><span class="term"><code class="filename">Xtranssock.c</code></span></p></td><td><p>
Socket implementation of the Transport Dependent API.
    </p></td></tr><tr><td><p><span class="term"><code class="filename">Xtranstli.c</code></span></p></td><td><p>
TLI implementation of the Transport Dependent API.
    </p></td></tr><tr><td><p><span class="term"><code class="filename">Xtransdnet.c</code></span></p></td><td><p>
DECnet implementation of the Transport Dependent API.
    </p></td></tr><tr><td><p><span class="term"><code class="filename">Xtranslocal.c</code></span></p></td><td><p>
Implementation of the Transport Dependent API for SYSV Local connections.
    </p></td></tr><tr><td><p><span class="term"><code class="filename">Xtrans.c</code></span></p></td><td><p>
Exposed Transport Independent API Functions.
    </p></td></tr><tr><td><p><span class="term"><code class="filename">Xtransutil.c</code></span></p></td><td><p>
Collection of Utility functions that use the X Transport Interface.
    </p></td></tr></tbody></table></div><p>
The file <code class="filename">Xtransint.h</code> contains much of the transport
related code that was previously in <code class="filename">Xlibint.h</code> and
<code class="filename">Xlibnet.h</code>.
This will make the definitions available for all transport users. This
should also obsolete the equivalent code in other libraries.
</p></div></div></body></html>