#define _POSIX_SOURCE
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <signal.h>

void sig_chld(int signo)
{
	pid_t pid;
	int stat;
	while ((pid = waitpid(-1, &stat, WNOHANG)) > 0) 
		printf("child %d terminated.\n", (int)pid);
	return ;
}

int main(int argc, char * argv[])
{
	int sockfd, rec_sock, i;
	int num;
	unsigned int len;
	struct sockaddr_in addr, recaddr;
	struct sigaction abc;
	char buf[100];

	abc.sa_handler = sig_chld;
	sigemptyset(&abc.sa_mask);
	abc.sa_flags = 0;

	sigaction(SIGCHLD, &abc, NULL);

	if (argc < 2) {
		printf("Usage: a.out port.\n");
		exit(0);
	}

	if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
		perror(": Can't get socket");
		exit(1);
	}

	addr.sin_addr.s_addr = INADDR_ANY;
	addr.sin_family = AF_INET;
	addr.sin_port = htons((short)atoi(argv[1]));

	if (bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
		perror(": bind");
		exit(1);
	}


	len = sizeof(addr);
	if (getsockname(sockfd, (struct sockaddr *)&addr, &len) < 0)
	{
		perror(": can't get name");
		_exit(1);
	}

	printf("ip = %s, port = %d\n", inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));

	if (listen(sockfd, 5) < 0) {
		perror(": bind");
		exit(1);
	}

	for (i=0; i<2; i++) { 
		if (fork() == 0) {
			while (1) {
				while ((rec_sock = accept(sockfd, (struct sockaddr *)(&recaddr), &len))
						< 0) {
					if (errno == EINTR) {
						printf("errno = %d\n", errno);
						continue; 
					} else {
						perror(":accept error");
						exit(1);
					}
				}

				/*
				if (rec_sock < 0) {
					perror(": accept");
					exit(1);
				}
				*/

				/* print the remote socket information */

				printf("remote machine = %s, port = %x, %x.\n",
						inet_ntoa(recaddr.sin_addr), recaddr.sin_port,
						ntohs(recaddr.sin_port)); 

				while ((num = read(rec_sock, buf, 100))) {
					if (num == -1)
						continue;
					write(rec_sock, buf, num);
				}
				close(rec_sock);  
			}
		}
	}
	while(1) { int i; wait(&i);}
}