A simple UNIX socket server

server.c

// You can test your server programs with 'telnet' UNIX tool.
// see man telnet!

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

int main(int argc, char *argv[])
{
  if (argc < 2)
    exit(1);

  // 1. Create a socket
  int listeningSocket = socket(AF_INET, SOCK_STREAM, 0);
  if (socket == -1) {
    perror("socket() error");
    exit(errno);
  }

  puts("Socket created");

  /* Enable address reuse */
  // If you don't do this, the system will prohibit reuse of the port for
  // some time, by default smth. about 3 minutes
  int on = 1;
  if (setsockopt(listeningSocket, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on))) {
    perror("setsockopt() error");
    exit(errno);
  }

  // 2. Bind the socket to an address
  struct sockaddr_in serverAddr;
  memset(&serverAddr, 0, sizeof(serverAddr));
  serverAddr.sin_family = AF_INET;
  serverAddr.sin_addr.s_addr = INADDR_ANY;
  serverAddr.sin_port = htons(atoi(argv[1]));
  // pitfall! Don't forget to cast the pointer into the correct type
  if (bind(listeningSocket, (struct sockaddr *) &serverAddr, sizeof(serverAddr))) {
    perror("bind() error");
    exit(errno);
  }
  puts("Adress binded");

  // 3. Make it listening
  if (listen(listeningSocket, 3)) {
    perror("listen() error");
    exit(errno);
  }

  // 4. Process clients
  for (;;) {
    puts("Waiting for a client...");
    int clientSocket;
    struct sockaddr_in clientAddress;
    socklen_t clientLen = sizeof(clientAddress);
    clientSocket = accept(listeningSocket, (struct sockaddr *) &clientAddress, &clientLen);
    if (clientSocket < 0) {
      perror("accept() error");
      exit(errno);
    }

    // While the client has smth to send, receive it and print on the screen
    char c;
    int recvStatus;
    while ((recvStatus = recv(clientSocket, &c, 1, 0)) > 0)
    {
      printf("%c\n", c);
    }
    if (recvStatus < 0) {
      perror("An error has occured");
      exit(errno);
    }

    puts("A client has been connected");
  }

  return 0;
}