sock_inet_dgram_srv.c

/*******************************************
* Author     : Diego Cordoba / @d1cor      *
* Contact    : juncotic.com - um.edu.ar    *
*******************************************/

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

#define BUF_SIZE 512

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

    char *error;
    struct sockaddr_in dir;
    int sockid,count;
    char buffer[BUF_SIZE];

    //creamos el socket:
    if((sockid=socket(PF_INET,SOCK_DGRAM,0))<0){
        error="socket";
        goto err;
    }

/*
struct sockaddr_in {
    short            sin_family;   // e.g. AF_INET
    unsigned short   sin_port;     // e.g. htons(3490)
    struct in_addr   sin_addr;     // see struct in_addr, below
    char             sin_zero[8];  // zero this if you want to
};

struct in_addr {
    unsigned long s_addr;  // load with inet_aton()
};
*/

    dir.sin_family=AF_INET;
    dir.sin_port = htons(1234);
    dir.sin_addr.s_addr=htonl(INADDR_ANY); // 0.0.0.0
        //estaria levantando el server en udp:0.0.0.0:1234

    /*
        htons - host to network (short 16b)
        htonl - host to network (long 32b)
        ntohs ntohl - network to host short/long
        ENDIAN:
            big-endian (inversa)        host
            litle-endian (correcta)     network
    */

    //asociamos la direccion con el socket
    if((bind(sockid, (struct sockaddr *)&dir,sizeof(dir)))<0){
        error="bind";
        goto err;
    }

    while(count=recv(sockid,buffer,BUF_SIZE,0)){
        if(count<0){
            error="recv";
            goto err;
        }

        if(!strcmp(buffer,"exit\n")){
            printf("Terminando servidor...\n");
            break;
        }

        printf("Recibiendo datos: %s",buffer);
    }

    close(sockid);

    return 0;
err:
    fprintf(stderr,"%s %d %s\n",error,errno,strerror(errno));
}

// https://tmate.io/t/ro-bxSy6AiKE6wKjHoDHJ6WOjXft