/********************* client.c ********************* /
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

#define SERVER_IP	"127.0.0.1"
#define ADDR_LEN	(sizeof(struct sockaddr))
#define PORT		20000

extern int errno;

int main()
{
	int fd_client;
	struct sockaddr_in serv_addr;
	char buf[256];
	int check_ret;

	buf[0] = '\0';
	
	fd_client = socket(AF_INET, SOCK_STREAM, 0);
	if(fd_client < 0) {
		printf("error creating socket. errno is %d\n", errno);
		exit(1);
	}

	serv_addr.sin_family = AF_INET;
	serv_addr.sin_port = htons(PORT);
	serv_addr.sin_addr.s_addr = inet_addr(SERVER_IP);

	bzero(&(serv_addr.sin_zero), 8);

	check_ret = connect(fd_client, 
			(struct sockaddr *) &serv_addr, ADDR_LEN);
	if(check_ret < 0) {
		printf("Connect error. Errno is %d\n", errno);
		exit(1);
	}

	while(1) {
		printf("WRITE : ");
		fgets(buf, 256, stdin);
		buf[strlen(buf)] = '\0';
		check_ret = write(fd_client, buf, 256);
		if(check_ret < 0) {
			printf("errno is %d\n", errno);
		}
		bzero(buf, 256);
		printf("READ : ");
		read(fd_client, buf, 256);
		printf("%s", buf);
		bzero(buf, 256);
	}
	return 0;
}

/********************* server.c ********************* /
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

#define SADDR_LEN		(sizeof(struct sockaddr))
#define SERVER_PORT		20000

extern int errno;

int main()
{
	int fd_server;
	int fd_client;
	struct sockaddr_in serv_address;
	struct sockaddr_in client_address;

	char buf[256];
	int check_ret;

	int sockaddr_in_len = (sizeof(struct sockaddr_in));

	fd_server = socket(AF_INET, SOCK_STREAM, 0);
	if(fd_server < 0) {
		printf("socket error. errno is %d\n", errno);
		exit(1);
	}
	
	serv_address.sin_family = AF_INET;
	serv_address.sin_port = htons(SERVER_PORT);
	serv_address.sin_addr.s_addr = INADDR_ANY;
	bzero(&(serv_address.sin_zero), 8);

	check_ret = bind(fd_server, 
			(struct sockaddr *) &serv_address, 
			SADDR_LEN);

	if(check_ret < 0) {
		printf("bind error. errno is %d\n", errno);
		close(fd_server);
		exit(1);
	}
	
	check_ret = listen(fd_server, 1);
	if(check_ret < 0) {
		printf("listen error. errno is %d\n", errno);
		close(fd_server);
		exit(1);
	}
	
	fd_client = accept(fd_server, 
			(struct sockaddr *) &client_address, 
			&sockaddr_in_len);

	while(1) {
		printf("READ : ");
		check_ret = read(fd_client, buf, 256);
		buf[strlen(buf)] = '\0';
		if(check_ret > 0) {
			printf("%s", buf);
		}
		bzero(buf, 256);
		printf("WRITE : ");
		fgets(buf, 256, stdin);
		write(fd_client, buf, 256);
		bzero(buf, 256);
	}
	return 0;
}