Question

I started to read and learn about “sockets”, but I’m looking for a small code-sample written in C for a client and server which will be non-blocking

The code should be able to send input from the client and the server must be able to receive the output in the non-blocking state, both should be in the non-blocking state.

I’ve read a lot in Google and books, YouTube, but nothing really helped.

This is my server:

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>

int main()
{
    int sock;
    int addr_len, bytes_read;
    char recv_data[1024];
    struct sockaddr_in server_addr , client_addr;


    if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        perror("Socket");
        exit(1);
    }

    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(5000);

    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    bzero(&(server_addr.sin_zero),8);


    if (bind(sock,(struct sockaddr *)&server_addr,
             sizeof(struct sockaddr)) == -1)
    {
        perror("Bind");
        exit(1);
    }

    addr_len = sizeof(struct sockaddr);

    printf("\nUDPServer Waiting for client on port 5000");
    fflush(stdout);

    while (1)
    {

        bytes_read = recvfrom(sock,recv_data,1024,0, (struct sockaddr *)&client_addr, &addr_len);  // <---- Here is the problem


        recv_data[bytes_read] = '\0';

        printf("\n(%s , %d) said : ",inet_ntoa(client_addr.sin_addr),
               ntohs(client_addr.sin_port));
        printf("%s", recv_data);
        fflush(stdout);

    }
    return 0;
}

Answer 1

I think you’re asking how to perform I/O on a non-blocking socket. Beej’s guide has been around for a long time; it covers all this and more, with good code samples.