hello_client.c

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

void error_handling(char *message);

int main(int argc, char const *argv[])
{
	int sock;
	struct sockaddr_in serv_addr;
	char message[30];
	int str_len;

	if(argc != 3){
		printf("Usage : %s <IP> <port> \n", argv[0]);
		exit(1);
	}

	sock = socket(PF_INET, SOCK_STREAM, 0);
	if(sock == -1)
		error_handling("socket() error");

	memset(&serv_addr, 0, sizeof(serv_addr));
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_addr.s_addr = inet_addr(argv[1]);
	serv_addr.sin_port = htons(atoi(argv[2]));

	if(connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr))==-1)
		error_handling("connect() error");

	str_len = read(sock, message, sizeof(message)-1);
    if(str_len == -1)
    	error_handling("read() error");

    printf("Message from server : %s \n", message);
    close(sock);
    return 0;
}

void error_handling(char *message)
{
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(1);
}