simple daytime client C code

 /* daytime.c:
  * A sample daytime client C code 
  * Example daytime client:
  */

 #include <stdio.h>

 #include <unistd.h>

 #include <stdlib.h>

 #include <errno.h>

 #include <string.h>

 #include <sys/types.h>

 #include <sys/stat.h>

 #include <sys/socket.h>

 #include <sys/un.h>

 #include <netinet/in.h>

 #include <arpa/inet.h> 
 /*
  * This function reports the error and
  * exits back to the shell:
  */
  static void displayError (const char *on_what) {
     fputs (strerror(errno),stderr);
     fputs (": ",stderr);
     fputs (on_what,stderr);
     fputc ('\n',stderr);
     exit (1);
  }

  int main (int argc,char **argv) {
     int z;
     char *srvr_addr = NULL;
     struct sockaddr_in adr_srvr;/* AF_INET */
     int len_inet; /* length */
     int s; /* Socket */
     struct servent *sp; /* Service entry */
     char dtbuf[128]; /* Date/Time info */

  /*
   * Use a server address from the command
   * line, if one has been provided.
   * Otherwise, this program will default
   * to using the arbitrary address
   * 127.0.0.:
   */


     if ( argc >= 2 ) {
        srvr_addr = argv[1]; // Addr on cmdline
     } 
     else {
        srvr_addr = "127.0.0.1"; // Use default address
     }
  
  /*
   * Lookup the daytime tcp service:
   */
     sp = getservbyname("daytime","tcp");
     if ( !sp ) {
        fputs("Unknown service: daytime tcp\n", stderr);
        exit(1);
     }

  /*
   * Create a server socket address:
   */
     memset(&adr_srvr,0,sizeof adr_srvr);
     adr_srvr.sin_family = AF_INET;
     adr_srvr.sin_port = sp->s_port;
     adr_srvr.sin_addr.s_addr =
     inet_addr(srvr_addr);

     if ( adr_srvr.sin_addr.s_addr == INADDR_NONE ) {
        displayError ("bad address.");
     }
     len_inet = sizeof adr_srvr;

  /*
   * Create a TCP/IP socket to use:
   */
     s = socket(PF_INET,SOCK_STREAM,0);
     if ( s == -1 ) {
        displayError("socket()");
     }
  /*
   * Connect to the server:
   */
     z = connect(s,&adr_srvr,len_inet);
     if ( z == -1 ) {
        displayError("connect(2)");
     }

  /*
   * Read the date/time info:
   */
     z = read(s,&dtbuf,sizeof dtbuf-1);
     if ( z == -1 ) {
        displayError("read(2)");
     }

  /*
   * Report the Date & Time:
   */
     dtbuf[z] = 0; /* null terminate string */

     printf("Date & Time is: %s\n",dtbuf);


  /*
   * Close the socket and exit:
   */
     close(s);
     putchar('\n');

     return 0;
  }

See Also:

updated daytime client example

Socket Concepts and sample codes

Advance Socket Concepts and sample codes