我试图通过UDP向特定端口的服务器发送字符串“HI”,然后接收响应。但是,当我使用recvfrom()尝试获取响应时,我被阻塞了。我尝试使用已连接的UDP,但得到以下错误:
UDP接收出错:连接被拒绝
这可能是什么原因呢?服务器不在我的控制范围内,但我知道它工作正常。
我添加了代码:
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, 0, 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), 0, p->ai_addr, 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, 0,(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;
recvfrom
将阻塞直到套接字上有消息可用,您确定服务器正在响应您的消息吗? - jschmier