TCP echo server-client

__tcp_echo_server_client__.md

TCP Echo Server-Client in C

• Works on Linux
• Only single client can connect at a time

client.c

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

int main() {

	struct sockaddr_in server_addr;

	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(3000);
	server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

	int sockfd;
	if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
		printf("couldn't create socket\n");
		return 1;
	}
	printf("socket created\n");

	if (connect(sockfd, (struct sockaddr *) &server_addr, sizeof(server_addr)) < 0) {
	printf("couldn't connect\n");
		return 1;
	}
	printf("connected to the server\n");

	char msg[100], server_msg[100];

	while (1) {
		printf("write message : ");
		scanf("%[^\n]%*c", msg);
		send(sockfd, msg, sizeof(msg), 0);

		memset(server_msg, 0, sizeof(server_msg));
		recv(sockfd, server_msg, sizeof(server_msg) , 0);
		printf("Server reply : %s\n", server_msg);

		if (strcmp(server_msg, "bye") == 0) {
			printf("exiting...\n");
			break;
		}
	}

	close(sockfd);

	return 0;
}

server.c

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

int main() {
	
	struct sockaddr_in server_addr;
	
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(3000);
  	server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    
	int sockfd;
	if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
		printf("couldn't create socket\n");
		return 1;
	}
	printf("socket created\n");

	if (bind(sockfd, (struct sockaddr *) &server_addr, sizeof(server_addr)) < 0) {
		printf("couldn't bind socket\n");
		return 1;
	}
	printf("bind at port 3000\n");
        
	if (listen(sockfd, 5) < 0) {
		printf("couldn't listen to socket\n");
		return 1;
	}
	printf("listening connection: 5\n");

	struct sockaddr_in client_addr;
	int client_addr_size = sizeof(client_addr);

	while (1) {
		int client_sockfd;
		if ((client_sockfd = accept(sockfd, (struct sockaddr *) &client_addr, &client_addr_size)) < 0) {
			printf("couldn't accept connection\n");
			return 1;
		}
		printf("accepted connection from %s\n", inet_ntoa(client_addr.sin_addr));

		char msg[100];

		while(1) {
			recv(client_sockfd, msg, sizeof(msg), 0);
			printf("msg recv = %s\n", msg);

			send(client_sockfd, msg, sizeof(msg), 0);

			if (strcmp(msg, "bye") == 0) {
				printf("exiting...\n");
				break;
			}
		}
        
		close(client_sockfd);
	}

	close(sockfd);

	return 0;
}

Short URL: https://git.io/tcp_echo_server_client