sendrecv.c

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

#define RECV_PORT 7550
#define RECV_IP "172.16.38.139"

int main(){

  int pid;
  pid = fork();

    if(pid == 0){

      printf("figlio\n");
      int sockfd;
      struct sockaddr_in recv_addr;
      extern int errno;
      int i,n;
      char line[100];

      if((sockfd=socket(AF_INET,SOCK_DGRAM,0)) <0){
        printf("\nErrore nell'apertura del socket");
        return -1;
      }

      memset( &recv_addr,0, sizeof(recv_addr));
      recv_addr.sin_family = AF_INET;
      recv_addr.sin_addr.s_addr = inet_addr(RECV_IP);
      recv_addr.sin_port = htons(RECV_PORT);

      printf("\nInserisci un numero ");
      scanf("%d",&n);

      for(i=0;i<10;++i){
        sprintf(line,"\n %d",i+n);
        printf("%s",line);
        sendto(sockfd, line, strlen(line)+1, 0, (struct sockaddr *)&recv_addr, sizeof(recv_addr));
      }
    }
  else{
    printf("padre\n");
    int sockfd;
    struct sockaddr_in recv_addr, send_addr;
    //extern int errno;
    socklen_t l = sizeof(send_addr);
    char line[100];

    if((sockfd=socket(AF_INET,SOCK_DGRAM,0)) <0)
    { printf("\nErrore nell'apertura del socket");
      return -1;
    }
    memset((char *) &recv_addr,0,sizeof(recv_addr));
    recv_addr.sin_family = AF_INET;
    recv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    recv_addr.sin_port = htons(RECV_PORT);

    if(bind(sockfd, (struct sockaddr *) &recv_addr, sizeof(send_addr))<0){
      printf("\nErrore nel binding. Errore %d \n",errno);
      return -1;
    }

    for(;;){
      recvfrom(sockfd, line, 99,0, (struct sockaddr *)&send_addr,&l);
      printf("%s",line);
    }
  }
}