sockets/us_xfr_sv.c

This is sockets/us_xfr_sv.c (Listing 57-3, page 1168), an example from the book, The Linux Programming Interface.

The source code file is copyright 2024, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

  Cover of The Linux Programming Interface
+/* us_xfr_sv.c
+
+   An example UNIX stream socket server. Accepts incoming connections
+   and copies data sent from clients to stdout.
+
+   See also us_xfr_cl.c.
+*/
 #include "us_xfr.h"
 #define BACKLOG 5
 
 int
 main(int argc, char *argv[])
 {
     struct sockaddr_un addr;
     int sfd, cfd;
     ssize_t numRead;
     char buf[BUF_SIZE];
 
     sfd = socket(AF_UNIX, SOCK_STREAM, 0);
     if (sfd == -1)
         errExit("socket");
 
     /* Construct server socket address, bind socket to it,
        and make this a listening socket */
 
+    /* For an explanation of the following check, see the errata notes for
+       pages 1168 and 1172 at http://www.man7.org/tlpi/errata/. */
+
+    if (strlen(SV_SOCK_PATH) > sizeof(addr.sun_path) - 1)
+        fatal("Server socket path too long: %s", SV_SOCK_PATH);
+
     if (remove(SV_SOCK_PATH) == -1 && errno != ENOENT)
         errExit("remove-%s", SV_SOCK_PATH);
 
     memset(&addr, 0, sizeof(struct sockaddr_un));
     addr.sun_family = AF_UNIX;
     strncpy(addr.sun_path, SV_SOCK_PATH, sizeof(addr.sun_path) - 1);
 
     if (bind(sfd, (struct sockaddr *) &addr, sizeof(struct sockaddr_un)) == -1)
         errExit("bind");
 
     if (listen(sfd, BACKLOG) == -1)
         errExit("listen");
 
     for (;;) {          /* Handle client connections iteratively */
 
         /* Accept a connection. The connection is returned on a new
            socket, 'cfd'; the listening socket ('sfd') remains open
            and can be used to accept further connections. */
 
         cfd = accept(sfd, NULL, NULL);
         if (cfd == -1)
             errExit("accept");
 
         /* Transfer data from connected socket to stdout until EOF */
 
         while ((numRead = read(cfd, buf, BUF_SIZE)) > 0)
             if (write(STDOUT_FILENO, buf, numRead) != numRead)
                 fatal("partial/failed write");
 
         if (numRead == -1)
             errExit("read");
 
         if (close(cfd) == -1)
             errMsg("close");
     }
 }

Note that, in most cases, the programs rendered in these web pages are not free standing: you'll typically also need a few other source files (mostly in the lib/ subdirectory) as well. Generally, it's easier to just download the entire source tarball and build the programs with make(1). By hovering your mouse over the various hyperlinked include files and function calls above, you can see which other source files this file depends on.

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