server.c

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

int PORT = 9003;

int main(int argc, char *argv[]) {
    if(argc > 1) {
        PORT = atoi(argv[1]);
    }
    else {
        printf("Using default port because argument [PORT] was not given\n");
    }

    int s, n, ns;
    
    struct sockaddr_in myAddr;
    bzero(&myAddr, sizeof(myAddr));

    myAddr.sin_family = AF_INET;
    myAddr.sin_addr.s_addr = INADDR_ANY;
    myAddr.sin_port = htons(PORT);

    struct sockaddr_in cliAddr;
    socklen_t len = sizeof(cliAddr);
    
    char buf[1025];

    s = socket(PF_INET, SOCK_STREAM, 0);
    if(s == -1) {
        printf("Error while creating a socket...\n");
        exit(1);
    }

    n = bind(s, (struct sockaddr *) &myAddr, sizeof(myAddr));
    if(n == -1) {
        printf("Error while binding...\n");
        exit(1);
    }

    n = listen(s, 5);
    if(n == -1) {
        printf("Error listening...\n");
        exit(1);
    }

    while(1) {
        printf("Waiting for client connection...\n");
        ns = accept(s, (struct sockaddr *) &cliAddr, &len);
        
        if(ns == -1) {
            printf("Error while accepting client connection...\n");
            exit(1);
        }

        printf("Client connected...\n");

        // Receive length of payload
        int length = 0;
        
        while((n = recv(ns, &length, sizeof(length), 0))) {
            if(n == -1) {
                printf("Error while receiving length...\n");
                close(ns);
            }

            n = recv(ns, buf, length, 0);
            if(n == -1) {
                printf("Error while receiving payload...\n");
                exit(1);
            }

            buf[length] = '\0';

            printf("%d\t%s\n", length, buf);
        }
        
        close(ns);
    }

    return 0;
}