echo server (fork)

fork_echo_server.cpp

#include <iostream>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <errno.h>
using namespace std;

int setup_listener()
{
  const unsigned int port = 1986;
  const int backlog = -1;

  int listener;

  struct sockaddr_in sin;
  if ( (listener = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) {
    perror("socket");
    exit(1);
  }

  memset(&sin, 0, sizeof(struct sockaddr_in));
  sin.sin_family = AF_INET;
  sin.sin_addr.s_addr = htonl(INADDR_ANY);
  sin.sin_port = htons(port);

  if (bind(listener, (struct sockaddr*)&sin, sizeof(struct sockaddr)) < 0) {
    perror("bind");
    close(listener);
    exit(1);
  }

  if (listen(listener, backlog) < 0) {
    perror("listen");
    close(listener);
    exit(1);
  }

  return listener;
}

void run_server(int listener)
{
  const int bufsize = 1024;
  int sock;
  struct sockaddr_in client;
  socklen_t len;
  pid_t pid;
  ssize_t recvlen;

  char buf[bufsize];
  while (1) {
    if ((sock = accept(listener, (struct sockaddr*)&client, &len)) < 0) {
      perror("accept");
      exit(1);
    }
    if ((pid = fork()) == 0) {
      close(listener);
      recvlen = recv(sock, buf, bufsize-1, 0);
      send(sock, buf, recvlen, 0);
      exit(1);
    }
    cout << "pid = " << pid << endl;
    close(sock);
  }
}

int main(int argc, const char* argv[])
{
  int listener = setup_listener();
  run_server(listener);
  return 0;
}