19  Couche 7 : sockets mode non connecté

• Un exemple de serveur :

  int initialisationSocketUDP(char *service){
  struct addrinfo precisions,*resultat,*origine;
  int statut;
  int s;
  
  /* Construction de la structure adresse */
  memset(&precisions,0,sizeof precisions);
  precisions.ai_family=AF_UNSPEC;
  precisions.ai_socktype=SOCK_DGRAM;
  precisions.ai_flags=AI_PASSIVE;
  statut=getaddrinfo(NULL,service,&precisions,&origine);
  if(statut<0){ perror("initialisationSocketUDP.getaddrinfo"); exit(EXIT_FAILURE); }
  struct addrinfo *p;
  for(p=origine,resultat=origine;p!=NULL;p=p->ai_next)
    if(p->ai_family==AF_INET6){ resultat=p; break; }
  
  /* Creation d'une socket */
  s=socket(resultat->ai_family,resultat->ai_socktype,resultat->ai_protocol);
  if(s<0){ perror("initialisationSocketUDP.socket"); exit(EXIT_FAILURE); }
  
  /* Options utiles */
  int vrai=1;
  if(setsockopt(s,SOL_SOCKET,SO_REUSEADDR,&vrai,sizeof(vrai))<0){
    perror("initialisationServeurUDPgenerique.setsockopt (REUSEADDR)");
    exit(EXIT_FAILURE);
    }
  if(setsockopt(s,SOL_SOCKET,SO_BROADCAST,&vrai,sizeof vrai)<0){
    perror("initialisationSocketUDP.setsockopt (BROADCAST)");
    exit(EXIT_FAILURE);
    }
  
  /* Specification de l'adresse de la socket */
  statut=bind(s,resultat->ai_addr,resultat->ai_addrlen);
  if(statut<0) { freeaddrinfo(origine); shutdown(s,SHUT_RDWR); return -1; }
  
  /* Liberation de la structure d'informations */
  freeaddrinfo(origine);
  
  return s;
  }
  

• Boucle de réception des messages UDP :

  int boucleServeurUDP(int s,int (*traitement)(unsigned char *,int,struct sockaddr_storage *)){
  while(1){
    struct sockaddr_storage adresse;
    socklen_t taille=sizeof(adresse);
    unsigned char message[MAX_UDP_MESSAGE];
    int nboctets=recvfrom(s,message,MAX_UDP_MESSAGE,0,(struct sockaddr *)&adresse,&taille);
    if(nboctets<0) return -1;
    if(traitement(message,nboctet,&adresse)<0) break;
    }
  return 0;
  }
  

• Programme principal :

  int main(void){
  int s=initialisationSocketUDP("4242");
  boucleServeurUDP(s,votreFonctionUDP);
  close(s);
  return 0;
  }