client.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>

void error(const char* msg) {
    perror(msg);
    exit(1);
}

int main(int argc, char *argv[]) {

    signal(SIGCHLD, SIG_IGN); // ignore SIGCHLD to prevent zombies


    if (argc < 3) error ("wrong number of args");

    int sockfd, portno, n;

    struct sockaddr_in serv_addr;
    struct hostent *server;

    portno = atoi(argv[2]);

    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) error("error opening socket");

    // server = (struct hostent *) getbyhostname(argv[1]); /// obselete

    if (!server) error("no such host");

    memset(&serv_addr, 0 , sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;

    //  copy server address from *server to serv_addr
    // bcopy((char *) server->h_addr,
    //  (char *) &serv_addr.sin_addr.s_addr,
    //  server->h_length);
    inet_pton(AF_INET, "127.0.0.1", &(serv_addr.sin_addr));

    serv_addr.sin_port = htons(portno);

    // check if connect to server
    if (connect(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
        error("problem connecting");

    printf("enter message:\n");

    char buffer[256];
    bzero(buffer, 256);

    fgets(buffer, 255, stdin);

    n = write(sockfd, buffer, strlen(buffer)); // send data to server

    if (n < 0) error("error writing to socket");

    bzero(buffer, 256);

    n = read(sockfd, buffer, 255); // get response from server

    printf("%s\n", buffer);

    close(sockfd);


}