ds

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

int main(int argc, char **argv){
    int n;
    char *remote_ip = "127.0.0.1";
    int remote_port;
    int host_sock;
    char msg[1000];
    int portset=0;

    struct sockaddr_in host_add;
    struct sockaddr_in remote_add;

    unsigned int host_len = sizeof(host_add);
    unsigned int remote_len;

    if(argc>1){
        perror("Zu viele Argumente!!!\n");
        return 0;
    }

    host_sock = socket(AF_INET, SOCK_DGRAM, 0);

    int flags = fcntl(host_sock, F_GETFL, 0);
    if (fcntl(host_sock, F_SETFL, flags | O_NONBLOCK) < 0 || fcntl(STDIN_FILENO, F_SETFL, flags | O_NONBLOCK) < 0) {
        printf("ERROR: fcntl() failed");
        return -1;
    }

    host_add.sin_family = AF_INET;
    host_add.sin_port = htons(0);
    host_add.sin_addr.s_addr = htonl(0);

    bind(host_sock, (struct sockaddr *)&host_add, sizeof(host_add));

    getsockname(host_sock, (struct sockaddr*)&host_add, &host_len);
    printf("\n");
    printf("Local port is: %d\n", (int) ntohs(host_add.sin_port));

    printf("Port des Kommunikationspartner: ");
    scanf("%i", &remote_port);

    remote_add.sin_family = AF_INET;
    remote_add.sin_port = remote_port;
    remote_add.sin_addr.s_addr = inet_addr(remote_ip);
    remote_len = sizeof(remote_add);

    while(1){
        if((n=read(STDIN_FILENO, msg, sizeof(msg)))<0){
            if(errno!=EWOULDBLOCK){
                printf("FEHLER (NICHT EWOULDBLOCK)");
            }
        }
        else {
            if(portset==0){
                portset=1;
                bzero(msg,1000);
                continue;
            }
            else{
                msg[n]='\0';
                sendto(host_sock, msg, 1000, 0, (struct sockaddr*)&remote_add, sizeof(remote_add));
                bzero(msg, 1000);
            }
        }

        if((n=recvfrom(host_sock, msg, sizeof(msg), 0, (struct sockaddr*)&remote_add, &remote_len))<0){
            if(errno!=EWOULDBLOCK){
                printf("FEHLER (NICHT EWOULDBLOCK)");
            }
        }
        else {
            printf("%s\n", msg);
            bzero(msg, 1000);
        }

        bzero(msg, 1000);
    }

    close(host_sock);
    return 0;
}