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

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

     memset(&srv_addr, , 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[]));

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

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

     cli_adr_sz = sizeof(cli_addr);

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

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

     close(srv_sock);
     return ;
 }

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

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

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

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

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

     while () {
         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 - );
         msg[str_len] = ;
         printf("Msg form srv : %s", msg);
     }

     close(sock);
     return ;
 }

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

Makefile

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