Editing Berkeley sockets (section)

===Client===
Programming a TCP client application involves the following steps:
* Creating a TCP socket.
* Connecting to the server (''connect()''), by passing a {{code|sockaddr_in}} structure with the {{code|sin_family}} set to {{mono|AF_INET}}, {{code|sin_port}} set to the port the endpoint is listening (in network byte order), and {{code|sin_addr}} set to the IP address of the listening server (also in network byte order).
* Communicating with the remote host with the API functions ''send()'' and ''recv()'', as well as with the general-purpose functions ''write()'' and ''read()''.
* Closing each socket that was opened after use with function ''close().''

<syntaxhighlight lang="c">
  #include <sys/types.h>
  #include <sys/socket.h>
  #include <netinet/in.h>
  #include <arpa/inet.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  
  int main(void)
  {
    struct sockaddr_in sa;
    int res;
    int SocketFD;

    SocketFD = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (SocketFD == -1) {
      perror("cannot create socket");
      exit(EXIT_FAILURE);
    }
  
    memset(&sa, 0, sizeof sa);
  
    sa.sin_family = AF_INET;
    sa.sin_port = htons(1100);
    res = inet_pton(AF_INET, "192.168.1.3", &sa.sin_addr);

    if (connect(SocketFD, (struct sockaddr *)&sa, sizeof sa) == -1) {
      perror("connect failed");
      close(SocketFD);
      exit(EXIT_FAILURE);
    }
  
    /* perform read write operations ... */
  
    close(SocketFD);
    return EXIT_SUCCESS;
  }

</syntaxhighlight>