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

void error_handling(char *msg);

int main(int argc, char *argv[])
{
    int sock_fd;
    struct sockaddr_in serv_addr;
    char message[30] = {0};
    int rcv_len;

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

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

    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr(argv[1]);// server‘s IP addr
    serv_addr.sin_port = htons(atoi(argv[2]));//port

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

    rcv_len = read(sock_fd, message, sizeof(message) - 1);
    if (rcv_len == -1)
        error_handling("read() error!");

    printf("Message from server: %s\n", message);
    printf("read length : %d\n",rcv_len);
    close(sock_fd);

    return 0;
}

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

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

void error_handling(char *msg);

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

    struct sockaddr_in serv_addr;
    struct sockaddr_in clnt_addr;
    socklen_t clnt_addr_size;

    char message[] = "This is a sample TCP?sserver!";

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

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

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

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

    if (listen(serv_sock_fd, 5) == -1)
        error_handling("listen() error");

    clnt_addr_size = sizeof(clnt_addr);
    clnt_sock_fd = accept(serv_sock_fd, (struct sockaddr*)&clnt_addr, &clnt_addr_size);
    if (clnt_sock_fd == -1)
        error_handling("accept() error");

    write(clnt_sock_fd, message, sizeof(message));
    close(clnt_sock_fd);
    close(serv_sock_fd);

    return 0;
}

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