sockets/id_echo_cl.c

This is sockets/id_echo_cl.c (Listing 60-3, page 1242), an example from the book, The Linux Programming Interface.

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

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/* id_echo_cl.c

   A client for the UDP "echo" service. This program sends each of its
   command-line arguments as a datagram to the server and echoes the
   contents of the datagrams that the server sends in response.

   See also id_echo_sv.c.
*/
#include "id_echo.h"
int
main(int argc, char *argv[])
{
    int sfd, j;
    size_t len;
    ssize_t numRead;
    char buf[BUF_SIZE];

    if (argc < 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s host msg...\n", argv[0]);

    /* Construct server address from first command-line argument */

    sfd = inetConnect(argv[1], SERVICE, SOCK_DGRAM);
    if (sfd == -1)
        fatal("Could not connect to server socket");

    /* Send remaining command-line arguments to server as separate datagrams */

    for (j = 2; j < argc; j++) {
        len = strlen(argv[j]);
        if (write(sfd, argv[j], len) != len)
            fatal("partial/failed write");

        numRead = read(sfd, buf, BUF_SIZE);
        if (numRead == -1)
            errExit("read");

        printf("[%ld bytes] %.*s\n", (long) numRead, (int) numRead, buf);
        /*FIXME: above: should use %zd here, and remove (long) cast */
    }

    exit(EXIT_SUCCESS);
}

 

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