This is sockets/is_seqnum_v2_cl.c, an example to accompany the book, The Linux Programming Interface.

This file is not printed in the book; it is the solution to Exercise 59-2:c (page 1237).

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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.


Download sockets/is_seqnum_v2_cl.c

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Function list (Bold in this list means a function is not static)

/* is_seqnum_v2_cl.c

   A simple Internet stream socket client. This server obtains a sequence
   number from the server.

   The program is the same as is_seqnum_cl.c, except that it uses the
   functions in our inet_sockets.c library to simplify the creation of a
   socket that connects to the server's socket.

   See also is_seqnum_v2_sv.c.
#include "is_seqnum_v2.h"
main(int argc, char *argv[])
    if (argc < 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s server-host [sequence-len]\n", argv[0]);

    int cfd = inetConnect(argv[1], PORT_NUM_STR, SOCK_STREAM);
    if (cfd == -1)
        fatal("inetConnect() failed");

    char *reqLenStr = (argc > 2) ? argv[2] : "1";
    if (write(cfd, reqLenStr, strlen(reqLenStr)) !=  strlen(reqLenStr))
        fatal("Partial/failed write (reqLenStr)");
    if (write(cfd, "\n", 1) != 1)
        fatal("Partial/failed write (newline)");

    char seqNumStr[INT_LEN];            /* Start of granted sequence */
    ssize_t numRead = readLine(cfd, seqNumStr, INT_LEN);
    if (numRead == -1)
    if (numRead == 0)
        fatal("Unexpected EOF from server");

    printf("Sequence number: %s", seqNumStr);   /* Includes '\n' */

    exit(EXIT_SUCCESS);                         /* Closes 'cfd' */


Download sockets/is_seqnum_v2_cl.c

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