#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <pthread.h>

#define BUF_SIZE 100
void * handle_clnt(void * arg);
void error_handling(char *buf);

char buf[BUF_SIZE];
pthread_mutex_t mutx;

int main(int argc, char *argv[])
{
	int serv_sock, clnt_sock;
	struct sockaddr_in serv_adr, clnt_adr;
	int clnt_adr_sz;
	pthread_t t_id;

	if(argc != 2) {
		printf("Usage : %s <port>\n", argv[0]);
		exit(1);
	}

	pthread_mutex_init(&mutx, NULL);
	serv_sock = socket(PF_INET, SOCK_STREAM, 0);
	memset(&serv_adr, 0, sizeof(serv_adr));
	serv_adr.sin_family = AF_INET;
	serv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
	serv_adr.sin_port = htons(atoi(argv[1]));
	
	if(bind(serv_sock, (struct sockaddr*) &serv_adr, sizeof(serv_adr)) == -1)
		error_handling("bind() error");
	if(listen(serv_sock, 5) == -1)
		error_handling("listen() error");

	while(1)
	{
		clnt_adr_sz = sizeof(clnt_adr);
		clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_adr,&clnt_adr_sz);
		pthread_create(&t_id, NULL, handle_clnt, (void*)&clnt_sock);
		pthread_detach(t_id);
		printf("Connected client IP: %s \n", inet_ntoa(clnt_adr.sin_addr));
	}

	close(serv_sock);
	return 0;
}

void * handle_clnt(void * arg)
{
	int clnt_sock = *((int*)arg);
	int str_len = 0;
	
	while(1)
	{
		pthread_mutex_lock(&mutx);
		str_len = read(clnt_sock, buf, sizeof(buf));
		if(str_len <= 0)
			break;
		else
			write(clnt_sock, buf, str_len);
		pthread_mutex_unlock(&mutx);
	}
	
	close(clnt_sock);
	return NULL;
}
void error_handling(char *buf)
{
	fputs(buf, stderr);
	fputc('\n', stderr);
	exit(1);
}