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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>t_open</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4>NAME</h4><blockquote>t_open - establish a transport endpoint</blockquote><h4>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="xti.h.html">xti.h</a>> #include <fcntl.h>int t_open( const char *name, int oflag, struct t_info *info)</code></pre></blockquote><h4>DESCRIPTION</h4><blockquote><pre><P><table bordercolor=#000000 border=1 align=center><tr valign=top><th align=center><b>Parameters</b><th align=center><b>Before call</b><th align=center><b>After call</b><tr valign=top><td align=left>name<td align=center>x<td align=center>=<tr valign=top><td align=left>oflag<td align=center>x<td align=center>=<tr valign=top><td align=left>info-><td align=center>addr<td align=center>/<tr valign=top><td align=left>info-><td align=center>options<td align=center>/<tr valign=top><td align=left>info-><td align=center>tsdu<td align=center>/<tr valign=top><td align=left>info-><td align=center>etsdu<td align=center>/<tr valign=top><td align=left>info-><td align=center>connect<td align=center>/<tr valign=top><td align=left>info-><td align=center>discon<td align=center>/<tr valign=top><td align=left>info-><td align=center>servtype<td align=center>/<tr valign=top><td align=left>info-><td align=center>flags<td align=center>/</table></pre><p>The<i>t_open()</i>function must be called as the first step in the initialisation of atransport endpoint.This function establishes a transport endpoint by supplying atransport provider identifier that indicates a particular transportprovider (that is, transport protocol) and returning a file descriptorthat identifies that endpoint.<p>The argument<I>name</I>points to a transport provider identifier and<I>oflag</I>identifies any open flags (as in<i><a href="../xsh/open.html">open()</a></i>).The argument<I>oflag</I>is constructed from O_RDWR optionally bitwise inclusive-OR'edwith O_NONBLOCK.These flags are defined by the header<B><fcntl.h></B>.The file descriptor returned by<i>t_open()</i>will be used by all subsequent functionsto identify the particular local transport endpoint.<p>This function also returns various default characteristics ofthe underlying transport protocolby setting fields in the<B>t_info</B>structure.This argument points to a<B>t_info</B>which contains the followingmembers:<pre><code>t_scalar_t addr; /* max size of the transport protocol address */t_scalar_t options; /* max number of bytes of */ /* protocol-specific options */t_scalar_t tsdu; /* max size of a transport service data */ /* unit (TSDU) */t_scalar_t etsdu; /* max size of an expedited transport */ /* service data unit (ETSDU) */t_scalar_t connect; /* max amount of data allowed on */ /* connection establishment functions */t_scalar_t discon; /* max amount of data allowed on */ /* t_snddis() and t_rcvdis() functions */t_scalar_t servtype; /* service type supported by the */ /* transport provider */t_scalar_t flags; /* other info about the transport provider */</code></pre><br><p>The values of the fields have the following meanings:<dl compact><dt><I>addr</I><dd>A value greater than zero (T_NULL) indicates the maximumsize of a transport protocol addressand a value of -2 (T_INVALID)specifies that the transport provider does not provide useraccess to transport protocol addresses.<dt><I>options</I><dd>A value greater than zero (T_NULL) indicates the maximumnumber of bytes of protocol-specific options supported by theprovider,and a value of -2 (T_INVALID) specifies that the transport providerdoes not support user-settable options.<dt><I>tsdu</I><dd>A value greater than zero (T_NULL) specifiesthe maximum size of a transport servicedata unit (TSDU);a value of zero (T_NULL) specifies that thetransport provider does not support the concept ofTSDU,although it does support the sending of a data stream with nological boundaries preserved across a connection;a value of -1 (T_INFINITE)specifies that there is no limit to the size of aTSDU;and a value of -2 (T_INVALID)specifies that the transfer of normal data isnot supported by the transport provider.<dt><I>etsdu</I><dd>A value greater than zero (T_NULL) specifiesthe maximum size of an expedited transportservice data unit (ETSDU);a value of zero (T_NULL) specifies that thetransport provider does not support the concept of ETSDU,although it does support the sending of an expedited data stream with nological boundaries preserved across a connection;a value of -1 (T_INFINITE) specifies that there is no limit on the size of anETSDU;and a value of -2 (T_INVALID)specifies that the transfer of expedited data isnot supported by the transport provider.Note that the semantics of expedited data may be quitedifferent for different transport providers(see<xref href=istpi></xref>and<xref href=ipsi></xref>).<dt><I>connect</I><dd>A value greater than zero (T_NULL) specifiesthe maximum amount of data that may be associated withconnection establishment functions,and a value of -2 (T_INVALID)specifies that the transport provider does notallow data to be sent with connection establishment functions.<dt><I>discon</I><dd>If the T_ORDRELDATA bit in flags is clear,a value greater than zero (T_NULL) specifiesthe maximum amount of data that may be associated with the<i><a href="t_snddis.html">t_snddis()</a></i>and<i><a href="t_rcvdis.html">t_rcvdis()</a></i>functions,and a value of -2 (T_INVALID)specifies that the transport provider does notallow data to be sent with the abortive release functions.If the T_ORDRELDATA bit is set in flags, a valuegreater than zero (T_NULL) specifies the maximum number of octetsthat may be associated with the <i><a href="t_sndreldata.html">t_sndreldata()</a></i>,<i><a href="t_rcvreldata.html">t_rcvreldata()</a></i>,<i><a href="t_snddis.html">t_snddis()</a></i>and <i><a href="t_rcvdis.html">t_rcvdis()</a></i>functions.<dt><I>servtype</I><dd>This field specifies the service type supported by the transport provider,as described below.<dt><I>flags</I><dd>This is a bit field used to specify other information about the communications provider. If the T_ORDRELDATA bit is set,the communications provider supports user data to be sentwith an orderly release.If the T_SENDZERO bit is set in flags, this indicates the underlyingtransport provider supports the sending of zero-length TSDUs.See<xref href=istpi></xref>for a discussion of the separate issue of zero-length fragmentswithin a TSDU.</dl><p>If a transport user is concerned with protocol independence, the abovesizes may be accessed to determine how large the buffers must beto hold each piece of information.Alternatively, the<i><a href="t_alloc.html">t_alloc()</a></i>function may be used to allocate these buffers.An error will result if a transport user exceeds the alloweddata size on any function.<p>The<I>servtype</I>field of<I>info</I>specifies one of the following values on return:<dl compact><dt>T_COTS<dd>The transport provider supports a connection-mode service butdoes not support the optional orderly release facility.<dt>T_COTS_ORD<dd>The transport provider supports a connection-mode service withthe optional orderly release facility.<dt>T_CLTS<dd>The transport provider supports a connectionless-mode service.For this service type,<i>t_open()</i>will return -2 (T_INVALID) for<I>etsdu</I>,<I>connect</I>and<I>discon</I>.</dl><p>A single transport endpoint may support only one of the aboveservices at one time.<p>If<I>info</I>is set toa null pointerby the transport user, no protocol information isreturned by<i>t_open()</i>.</blockquote><h4>VALID STATES</h4><blockquote>T_UNINIT</blockquote><h4>ERRORS</h4><blockquote>On failure,<I>t_errno</I>is set to the following:<dl compact><dt>[TBADFLAG]<dd>An invalid flag is specified.<dt>[TBADNAME]<dd>Invalid transport provider name.<dt>[TPROTO]<dd>This error indicates that a communication problem has been detected betweenXTI and the transport provider for which there is no other suitable XTIerror<I>(t_errno)</I>.<dt>[TSYSERR]<dd>A system error has occurred during execution of this function.</dl></blockquote><h4>RETURN VALUES</h4><blockquote>A valid file descriptor is returned upon successful completion. Otherwise,a value of -1 is returned and<I>t_errno</I>is set to indicate an error.</blockquote><h4>SEE ALSO</h4><blockquote><i><a href="../xsh/open.html">open()</a></i>.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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