echo-server.c

#include <stdio.h> // standard in-out
#include <errno.h> // error message
#include <unistd.h> // close function
#include <string.h>

#include <sys/socket.h> // socket
#include <netinet/in.h> // network address
#include <arpa/inet.h> // convert port number

int main(int argc, char **argv){

    // create socket
    int sock = socket(AF_INET,SOCK_STREAM,0);
    if(sock < 0){
        fprintf(stderr, "Error: Cannot create socket, %s\n", strerror(errno));
        return 1;
    }

    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8082);
    addr.sin_addr.s_addr = INADDR_ANY;

    int ret = 0;
    int reuse = 1;
    ret = setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse));
    if(ret == -1){
        fprintf(stderr, "Error: Cannot set socket option, %s\n", strerror(errno));
        return 1;
    }

    ret = bind(sock, (struct sockaddr *) &addr, sizeof(addr));
    if(ret < 0){
        fprintf(stderr, "Error: Couldn't bind socket, %s\n", strerror(errno));
        return 1;
    }


    ret = listen(sock, 10);
    if(ret < 0){
        fprintf(stderr, "Error: Too lound, could not listen. %s\n", strerror(errno));
        return 1;
    }

    printf("server is running at 127.0.0.1:8082\n");

    while(1){
        int client = accept(sock, NULL, NULL);
        printf("client connected\n");
        if(client < 0){
            fprintf(stderr, "Error: accept: %s\n", strerror(errno));
            break;
        }

        char buff[256] = {0};
        size_t r = recv(client, buff, sizeof(buff), 0);

        if(r < 0){
            fprintf(stderr, "Error: recv: %s\n", strerror(errno));
            break;
        }
        printf("RECV: %.*s", r, buff);
        while(r > 0){

            size_t s = send(client, buff, r, MSG_NOSIGNAL);
            if(s < 0){
                fprintf(stderr, "Error: send: %s\n", strerror(errno));
                break;
            }

            r = recv(client, buff, sizeof(buff), 0);
            if(r < 0){
                fprintf(stderr, "Error: recv: %s\n", strerror(errno));
                break;
            }
            if(r == 0){
                break;
            }
            printf("RECV: %.*s", r, buff);
        }

        ret = shutdown(client, SHUT_RDWR);
        if(ret < 0){
            fprintf(stderr, "Error: shutdown: %s\n", strerror(errno));
        }
        close(client);
        printf("client disconnected.\n");
    }

    shutdown(sock,SHUT_RDWR);
    close(sock);

    printf("exiting\n");

    return 0;
}