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

using namespace std;

const unsigned port = 5100;
const unsigned MAXBUFLEN = 512;


int main() {
    int serv_sockfd, cli_sockfd;
    struct sockaddr_in serv_addr, cli_addr;
    socklen_t sock_len;
    pid_t child_pid;
    ssize_t n;
    char buf[MAXBUFLEN];

    cout << "port = " << port << endl;
    serv_sockfd = socket(AF_INET, SOCK_STREAM, 0);
    
    bzero((void*)&serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(port);

    bind(serv_sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
    
    listen(serv_sockfd, 5);

    for (; ;) {
	sock_len = sizeof(cli_addr);
	cli_sockfd = accept(serv_sockfd, (struct sockaddr *)&cli_addr, &sock_len);
	
	if ((child_pid = fork()) == 0) {
	    close(serv_sockfd);
	    while ((n = read(cli_sockfd, buf, MAXBUFLEN)) > 0) {
		buf[n] = '\0';
		cout << buf << endl;
		write(cli_sockfd, buf, strlen(buf));
	    }
	    if (n == 0) {
		cout << "client closed" << endl;
	    } else {
		cout << "something wrong" << endl;
	    }
	    close(cli_sockfd);
	    exit(0);
	}
	close(cli_sockfd);
    }
}