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Taken from the original at http://www.ecst.csuchico.edu/~beej/guide/net/ ... see end of writeup for Copyright statement.

A Simple Stream Server

All this server does is send the string "Hello, World!\n" out over a stream connection. All you need to do to test this server is run it in one window, and telnet to it from another with:

$ telnet remotehostname 3490

where remotehostname is the name of the machine you're running it on.

The server code: (Note: a trailing backslash on a line means that the line is continued on the next.)

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>

#define MYPORT 3490    /* the port users will be connecting to */

#define BACKLOG 10     /* how many pending connections queue will hold */

  int sockfd, new_fd;  /* listen on sock_fd, new connection on new_fd */
  struct sockaddr_in my_addr;    /* my address information */
  struct sockaddr_in their_addr; /* connector's address information */
  int sin_size;

  if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {

  my_addr.sin_family = AF_INET;         /* host byte order */
  my_addr.sin_port = htons(MYPORT);     /* short, network byte order */
  my_addr.sin_addr.s_addr = INADDR_ANY; /* auto-fill with my IP */
  bzero(&(my_addr.sin_zero), 8);        /* zero the rest of the struct */

  if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {

  if (listen(sockfd, BACKLOG) == -1) {

  while(1) {  /* main accept() loop */
    sin_size = sizeof(struct sockaddr_in);
    if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, \
         &sin_size)) == -1) {
  printf("server: got connection from %s\n", \
  if (!fork()) { /* this is the child process */
    if (send(new_fd, "Hello, world!\n", 14, 0) == -1)
    close(new_fd);  /* parent doesn't need this */

    while(waitpid(-1, NULL, WNOHANG) > 0); /* clean up child processes */

In case you're curious, I have the code in one big main() function for (I feel) syntactic clarity. Feel free to split it into smaller functions if it makes you feel better.

You can also get the string from this server by using the client listed in the next section.

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Copyright © 1995, 1996 by Brian "Beej" Hall. This guide may be reprinted in any medium provided that its content is not altered, it is presented in its entirety, and this copyright notice remains intact. Contact beej@ecst.csuchico.edu for more information.

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