Server example

gistfile1.c

#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>

#define MAXPENDING 5
#define BUFFSIZE 32

void Die(char *mess) { perror(mess); exit(1); }

void HandleClient(int sock)
{
  char buffer[BUFFSIZE];
  int received = -1;

  if ((received = recv(sock, buffer, BUFFSIZE, 0)) < 0)
    {
      Die("Failed to receive initial bytes from client");
    }

  while (received > 0)
    {
      if (send(sock, buffer, received, 0) != received)
	{
	  Die ("Failed to send bytes to client");
	}
      
      if ((received = recv(sock, buffer, BUFFSIZE, 0)) < 0)
	{
	  Die("Failed to receive additional bytes from client");
	}

      close(sock);
    }

}

int main(int argc, char *argv[])
{
  int serversock, clientsock;
  struct sockaddr_in echoserver, echoclient;

  if (argc != 2)
    {
      fprintf(stderr, "USAGE: server <port>\n");
      exit(1);
    }

  if ((serversock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
    {
      Die("Failed to create socket");
    }
  
  memset(&echoserver, 0, sizeof(echoserver));
  echoserver.sin_family = AF_INET;
  echoserver.sin_addr.s_addr = htonl(INADDR_ANY);
  echoserver.sin_port = htons(atoi(argv[1]));

  if (bind(serversock, (struct sockaddr *) &echoserver, sizeof(echoserver)) < 0)
    {
      Die("Failed to bind the server socket");
    }

  if (listen(serversock, MAXPENDING) < 0)
    {
      Die("Failed to listen on server socket");
    }

  while (1)
    {
      unsigned int clientlen = sizeof(echoclient);
      if ((clientsock = accept(serversock, (struct sockaddr *) &echoclient, &clientlen)) < 0)
	{
	  Die("Failed to accept client connection");
	}
      
      fprintf(stdout, "Client connected: %s\n", inet_ntoa(echoclient.sin_addr));
      HandleClient(clientsock);
    }
}