linux_c_tcp_example

server

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


#define BUF_SIZE 1024

void err_handler(char *msg);

int main(int argc, char **argv) {
    int srv_sock, cli_sock;
    char msg[BUF_SIZE];
    int str_len;

    struct sockaddr_in srv_addr, cli_addr;
    socklen_t cli_adr_sz;

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

    srv_sock = socket(PF_INET, SOCK_STREAM, 0);
    if (srv_sock == -1) {
        err_handler("socket() error");
    }

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

    if (bind(srv_sock, (struct sockaddr *) &srv_addr, sizeof(srv_addr)) == -1) {
        err_handler("bind() error");
    }

    if (listen(srv_sock, 5) == -1) {
        err_handler("listen() error");
    }

    cli_adr_sz = sizeof(cli_addr);

    for (int i = 0; i < 5; ++i) {
        cli_sock = accept(srv_sock, (struct sockaddr *) &cli_addr, &cli_adr_sz);
        if (cli_sock == -1) {
            err_handler("accept() error");
        } else {
            printf("connected client %d\n", i + i);
        }

        while ((str_len = read(cli_sock, msg, BUF_SIZE)) != 0) {
            write(cli_sock, msg, str_len);
        }
        close(cli_sock);
    }

    close(srv_sock);
    return 0;
}

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

client

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


#define BUF_SIZE 1024

void err_handler(char *msg);

int main(int argc, char **argv) {
    int sock;
    char msg[BUF_SIZE];
    int str_len;
    struct sockaddr_in srv_addr;

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

    sock = socket(PF_INET, SOCK_STREAM, 0);
    if (sock == -1) {
        err_handler("socket() error");
    }

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

    if (connect(sock, (struct sockaddr *) &srv_addr, sizeof(srv_addr)) == -1) {
        err_handler("connect() error");
    } else {
        printf("connected .........");
    }

    while (1) {
        fputs("Input msg(Q to quit):", stdout);
        fgets(msg, BUF_SIZE, stdin);
        if (!strcmp(msg, "q\n") || !strcmp(msg, "Q\n")) {
            break;
        }
        write(sock, msg, strlen(msg));
        str_len = read(sock, msg, BUF_SIZE - 1);
        msg[str_len] = 0;
        printf("Msg form srv : %s", msg);
    }

    close(sock);
    return 0;
}

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

Makefile

all a_b:
    gcc -o srv main.c -g -Wall
    gcc -o cli client.c -g -Wall