我试图通过UDP在特定端口发送字符串HI到服务器,然后接收响应.但是,在尝试使用recvfrom()获取响应后,我被卡在阻塞状态.我尝试使用连接的UDP,但我得到：
Error receiving in UDP: Connection refused
这可能是什么原因？服务器不在我的控制之下,但我知道它的工作正常.
int sockfdudp;
char bufudp[MAXDATASIZE],port[6];
struct addrinfo hints,*servinfo,*p;
struct sockaddr_storage addr;
int rv;
char s[INET6_ADDRSTRLEN];
int bytes_recv,bytes_sent;
socklen_t len;
scanf("%s",port);
printf("UDP Port: %s \n",port);
// Start connecting to datagram server
memset(&hints,sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
if ((rv = getaddrinfo(SERVER_NAME,port,&hints,&servinfo)) != 0) {
fprintf(stderr,"getaddrinfo: %s\n",gai_strerror(rv));
return 1;
}
// loop through all the results and make a socket
for(p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfdudp = socket(p->ai_family,p->ai_socktype,p->ai_protocol)) == -1) {
perror("Creating datagram socket");
continue;
}
if (connect(sockfdudp,p->ai_addr,p->ai_addrlen) == -1) {
close(sockfdudp);
perror("Connecting stream socket");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr,"ClientUDP: Failed to bind socket\n");
return 2;
}
freeaddrinfo(servinfo);
if ((bytes_sent = sendto(sockfdudp,UDP_MSG,strlen(UDP_MSG),p->ai_addrlen)) == -1) {
perror("ClientUDP: Error sending data");
exit(1);
}
printf("Data %s sent\n",UDP_MSG );
len = sizeof(struct sockaddr_storage);
if ((bytes_recv = recvfrom(sockfdudp,bufudp,MAXDATASIZE-1,(struct sockaddr*)&addr,&len)) == -1) {
perror("Error receiving in UDP");
exit(1);
}
printf("Bytes recv %d\n",bytes_recv);
bufudp[bytes_recv] = '\0';
printf("ClientUDP: Received\n %s \n",bufudp );
close(sockfdudp);
return 0;
