#include  "unp.h"

  int
  main(int argc, char **argv)
  {
      int     sockfd, n;
      char    recvline[MAXLINE + 1];
      struct sockaddr_in servaddr;

      if (argc != 2)
          err_quit("usage: a.out <IPaddress>");

     if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
         err_sys("socket error");

     bzero(&servaddr, sizeof(servaddr));
     servaddr.sin_family = AF_INET;
     servaddr.sin_port = htons(13);  /* daytime server */
     if (inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0)
         err_quit("inet_pton error for %s", argv[1]);

     if (connect(sockfd, (SA *) &servaddr, sizeof(servaddr)) < 0)
         err_sys("connect error");

     while ( (n = read(sockfd, recvline, MAXLINE)) > 0) {
         recvline[n] = 0;        /* null terminate */
         if (fputs(recvline, stdout) == EOF)
             err_sys("fputs error");
     }
     if (n < 0)
         err_sys("read error");

     exit(0);
 }

root@ubuntu:/home/jack/dev/practice# ./daytimetcpcli 192.168.0.109
connect error: Connection refused
root@ubuntu:/home/jack/dev/practice#

jack@ubuntu:~$ sudo netstat -tlp

  activate Internet connection (just server)
  Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
  tcp        0      0 localhost:5038          *:*                     LISTEN      1625/asterisk
  tcp        0      0 *:cisco-sccp            *:*                     LISTEN      1625/asterisk
  tcp        0      0 *:http                  *:*                     LISTEN      1679/apache2
  tcp        0      0 localhost:domain        *:*                     LISTEN      1405/dnsmasq
  tcp        0      0 localhost:ipp           *:*                     LISTEN      933/cupsd
  tcp        0      0 localhost:postgresql    *:*                     LISTEN      1076/postgres
  tcp        0      0 localhost:5946          *:*                     LISTEN      983/teamviewerd
  tcp        0      0 *:sip                   *:*                     LISTEN      1625/asterisk
  tcp6       0      0 ip6-localhost:ipp       [::]:*                  LISTEN      933/cupsd

service daytime
{
    disable         = no
    type            = INTERNAL
    id              = daytime-stream
    socket_type     = stream
    protocol        = tcp
    user            = root
    wait            = no
}