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<!-- Copyright (C) 2003 Red Hat, Inc. --> <!-- This material may be distributed only subject to the terms --> <!-- and conditions set forth in the Open Publication License, v1.0 --> <!-- or later (the latest version is presently available at --> <!-- http://www.opencontent.org/openpub/). --> <!-- Distribution of the work or derivative of the work in any --> <!-- standard (paper) book form is prohibited unless prior --> <!-- permission is obtained from the copyright holder. --> <HTML ><HEAD ><TITLE >Sockets</TITLE ><meta name="MSSmartTagsPreventParsing" content="TRUE"> <META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="eCos Reference Manual" HREF="ecos-ref.html"><LINK REL="UP" TITLE="File System Support Infrastructure" HREF="fileio.html"><LINK REL="PREVIOUS" TITLE="Initialization and Mounting" HREF="fileio-mounting.html"><LINK REL="NEXT" TITLE="Select" HREF="fileio-select.html"></HEAD ><BODY CLASS="CHAPTER" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >eCos Reference Manual</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="fileio-mounting.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="fileio-select.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="CHAPTER" ><H1 ><A NAME="FILEIO-SOCKETS">Chapter 26. Sockets</H1 ><P >If a network stack is present, then the FILEIO infrastructure also provides access to the standard BSD socket calls.</P ><P >The netstack table contains entries which describe the network protocol stacks that are in the system image. Each resident stack should export an entry to this table using the <TT CLASS="LITERAL" >NSTAB_ENTRY()</TT > macro.</P ><P >Each table entry has the following structure:</P ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="PROGRAMLISTING" >struct cyg_nstab_entry { cyg_bool valid; // true if stack initialized cyg_uint32 syncmode; // synchronization protocol char *name; // stack name char *devname; // hardware device name CYG_ADDRWORD data; // private data value int (*init)( cyg_nstab_entry *nste ); int (*socket)( cyg_nstab_entry *nste, int domain, int type, int protocol, cyg_file *file ); };</PRE ></TD ></TR ></TABLE ><P >This table is analogous to a combination of the filesystem and mount tables.</P ><P >The <TT CLASS="STRUCTFIELD" ><I >valid</I ></TT > field is set <TT CLASS="LITERAL" >true</TT > if the stack's <TT CLASS="FUNCTION" >init()</TT > function returned successfully and the <TT CLASS="STRUCTFIELD" ><I >syncmode</I ></TT > field contains the <TT CLASS="LITERAL" >CYG_SYNCMODE_SOCK_*</TT > bits described above.</P ><P >The <TT CLASS="STRUCTFIELD" ><I >name</I ></TT > field contains the name of the protocol stack.</P ><P >The <TT CLASS="STRUCTFIELD" ><I >devname</I ></TT > field names the device that the stack is using. This may reference a device under "/dev", or may be a name that is only meaningful to the stack itself.</P ><P >The <TT CLASS="FUNCTION" >init()</TT > function pointer is called during system initialization to start the protocol stack running. If it returns non-zero the <TT CLASS="STRUCTFIELD" ><I >valid</I ></TT > field is set false and the stack will be ignored subsequently.</P ><P >The <TT CLASS="FUNCTION" >socket()</TT > function is called to attempt to create a socket in the stack. When the <TT CLASS="FUNCTION" >socket()</TT > API function is called the netstack table is scanned and for each valid entry the <TT CLASS="FUNCTION" >socket()</TT > function pointer is called. If this returns non-zero then the scan continues to the next valid stack, or terminates with an error if the end of the table is reached.</P ><P >The result of a successful socket call is an initialized file object with the <TT CLASS="STRUCTFIELD" ><I >f_xops</I ></TT > field pointing to the following structure:</P ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="PROGRAMLISTING" >struct cyg_sock_ops { int (*bind) ( cyg_file *fp, const sockaddr *sa, socklen_t len ); int (*connect) ( cyg_file *fp, const sockaddr *sa, socklen_t len ); int (*accept) ( cyg_file *fp, cyg_file *new_fp, struct sockaddr *name, socklen_t *anamelen ); int (*listen) ( cyg_file *fp, int len ); int (*getname) ( cyg_file *fp, sockaddr *sa, socklen_t *len, int peer ); int (*shutdown) ( cyg_file *fp, int flags ); int (*getsockopt)( cyg_file *fp, int level, int optname, void *optval, socklen_t *optlen); int (*setsockopt)( cyg_file *fp, int level, int optname, const void *optval, socklen_t optlen); int (*sendmsg) ( cyg_file *fp, const struct msghdr *m, int flags, ssize_t *retsize ); int (*recvmsg) ( cyg_file *fp, struct msghdr *m, socklen_t *namelen, ssize_t *retsize ); };</PRE ></TD ></TR ></TABLE ><P >It should be obvious from the names of these functions which API calls they provide support for. The <TT CLASS="FUNCTION" >getname()</TT > function pointer provides support for both <TT CLASS="FUNCTION" >getsockname()</TT > and <TT CLASS="FUNCTION" >getpeername()</TT > while the <TT CLASS="FUNCTION" >sendmsg()</TT > and <TT CLASS="FUNCTION" >recvmsg()</TT > function pointers provide support for <TT CLASS="FUNCTION" >send()</TT >, <TT CLASS="FUNCTION" >sendto()</TT >, <TT CLASS="FUNCTION" >sendmsg()</TT >, <TT CLASS="FUNCTION" >recv()</TT >, <TT CLASS="FUNCTION" >recvfrom()</TT > and <TT CLASS="FUNCTION" >recvmsg()</TT > as appropriate.</P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="fileio-mounting.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ecos-ref.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="fileio-select.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Initialization and Mounting</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="fileio.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Select</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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