好的，基本上我的应用程序每隔一两秒就会有一个运行循环，同时我还有另一个线程正在循环通过该listenForPackets方法；broadcastMessage仅在发生另一种操作方法时才启动。这个问题的重要部分是，当侦听器线程与主线程分开运行时，它永远不会打印出任何打印命令，而且它似乎不允许访问我定义的名为的全局变量，该变量recvMessage位于接口和实现部分。
在我的代码中，我对其进行了设置，以便每次运行主运行循环时，它都会更新我的 GUI 中的 UILabel。当应用程序运行时，我的标签一直保持空白并且永远不会改变。我已经仔细检查了 GUI，所有内容都正确链接在那里，我的标签也被正确实例化（我在下面的代码中使用名称“标签”作为 UILabel 的实例）。有人知道为什么我的标签会更新吗？我相信事物的网络方面很好，因为我刚刚完成了，一切都在“交谈”。也许这是一个我不知道的变量范围问题，或者是否允许单独的线程访问全局变量，例如我在下面使用的那个（rcvMessage）？我对多线程应用程序相当陌生，但我不相信它真的很难实现，
全局变量
NSString *recvMessage;
Main Runloop - 每次通过 runloop 时更新标签的部分
if (label.text != recvMessage)
label.text = recvMessage
说话者法
-(void)broadcastMessage { // (NSString*)msg {
msg = @"From_Master";
NSLog(@"broadcastMessage - Stage 1");
mc_ttl = 15; // number of node hops the message is allowed to travel across the network
// define the port we will be using
mc_port = MYPORT;
// create a socket for sending to the multicast address
if ((sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
NSLog(@"ERROR: broadcastMessage - socket() failed");
return;
}
memset(&mc_addr, 0, sizeof(mc_addr));
mc_addr.sin_family = AF_INET;
mc_addr.sin_addr.s_addr = inet_addr(GROUP_ADDRESS);
mc_addr.sin_port = htons(MYPORT);
NSLog(@"broadcastMessage - Stage 2");
// set the TTL (time to live/hop count) for the send
if ((setsockopt(sock, IPPROTO_IP, IP_MULTICAST_TTL, &mc_ttl, sizeof(mc_ttl))) < 0) {
NSLog(@"ERROR: broadcastMessage - setsockopt() failed");
return;
}
NSLog(@"broadcastMessage - Stage 3");
// clear send buffer
memset(send_str, 0, sizeof(send_str));
// convert the message to a C string to send
[msg getCString:send_str maxLength:MAX_LEN encoding:NSASCIIStringEncoding];
//while (fgets(send_str, MAX_LEN, stdin)) {
NSLog(@"broadcastMessage - Stage 4");
NSLog(@"Message =");
printf(send_str);
// send string to multicast address
if ((sendto(sock, send_str, sizeof(send_str), 0, (struct sockaddr *)&mc_addr, sizeof(mc_addr))) < 0) {
NSLog(@"ERROR: broadcastMessage - sendto() sent incorrect number of bytes");
//return;
}
NSLog(@"Sent Message -");
printf(send_str);
NSLog(@"broadcastMessage - Stage 5");
// clear send buffer
memset(send_str, 0, sizeof(send_str));
NSLog(@"broadcastMessage - Stage 6 - Complete");
close(sock);
}
侦听器方法
-(void)listenForPackets {
listeningFlag_on = 1; // allows reuse of the same socket
NSLog(@"listenForPackets - Stage 1");
if ((listeningSock = socket(AF_INET, SOCK_DGRAM,IPPROTO_UDP)) < 0) {
NSLog(@"ERROR: listenForPackets - socket() failed");
return;
// make the method return an int instead of void and use this statement to check for errors
}
NSLog(@"listenForPackets - Stage 2");
// set reuse port to on to allow multiple binds per host
if ((setsockopt(listeningSock, SOL_SOCKET, SO_REUSEADDR, &listeningFlag_on, sizeof(listeningFlag_on))) < 0) {
NSLog(@"ERROR: listenForPackets - setsockopt() Reuse failed");
return;
// make the method return an int instead of void and use this statement to check for errors
}
// construct a multicast address structure after erasing anything in the listeningmc_addr structure
memset(&listeningmc_addr, 0, sizeof(listeningmc_addr));
listeningmc_addr.sin_family = AF_INET;
listeningmc_addr.sin_addr.s_addr = htonl(INADDR_ANY); // different from sender
listeningmc_addr.sin_port = htons(MYPORT);
// bind multicast address to socket
if ((bind(listeningSock, (struct sockaddr *)&listeningmc_addr, sizeof(listeningmc_addr))) < 0) {
NSLog(@"ERROR: listenForPackets - bind() failed");
perror("Bind() -");
return; // make the method return an int instead of void and use this statement to check for errors
}
//*********************************************************************************
NSString *ipAddress = [[NSString alloc] initWithString:self.getIPAddress];
const char *tmp = [ipAddress UTF8String];
listeningMc_addr_str = tmp;
printf("%s\n", listeningMc_addr_str);
listeningMc_req.imr_multiaddr.s_addr = inet_addr(GROUP_ADDRESS);
listeningMc_req.imr_interface.s_addr = htonl(INADDR_ANY);
// send an ADD MEMBERSHIP message via setsockopt
if ((setsockopt(listeningSock, IPPROTO_IP, IP_ADD_MEMBERSHIP, &listeningMc_req, sizeof(listeningMc_req))) < 0) {
NSLog(@"ERROR: listenForPackets - setsockopt() failed");
int err = errno;
NSLog(@"errno - %i", err);
NSLog(@"Error = %s", strerror(err));
perror("ERROR");
return; // make the method return an int instead of void and use this statement to check for errors
}
NSLog(@"listenForPackets - Stage 3");
for (;;) { // loop forever
// clear the receive buffers & structs
memset(listeningRecv_str, 0, sizeof(listeningRecv_str));
listeningFrom_len = sizeof(listeningFrom_addr);
memset(&listeningFrom_addr, 0, listeningFrom_len);
NSLog(@"Test #1 Complete");
//msgStatus.text = @"Waiting...";
// block waiting to receive a packet
listeningFrom_len = sizeof(listeningmc_addr);
if ((listeningRecv_len = recvfrom(listeningSock, listeningRecv_str, MAX_LEN, 0, (struct sockaddr*)&listeningmc_addr, &listeningFrom_len)) < 0) {
NSLog(@"ERROR: listenForPackets - recvfrom() failed");
return; // make the method return an int instead of void and use this statement to check for errors
}
NSLog(@"Test #2 Complete - Received a Message =");
NSLog(@"listenForPackets - Stage 4");
// listeningRecv_str
**tmpString = [[NSString alloc] initWithCString:listeningRecv_str encoding:NSASCIIStringEncoding];
NSLog(@"Message Received =");
NSLog(tmpString);
recvMessage = tmpString;**
//}
// received string
printf("Received %d bytes from %s: ", listeningRecv_len, inet_ntoa(listeningFrom_addr.sin_addr));
printf("%s", listeningRecv_str);
//}
}
// send a DROP MEMBERSHIP message via setsockopt
if ((setsockopt(listeningSock, IPPROTO_IP, IP_DROP_MEMBERSHIP, (void*) &listeningMc_req, sizeof(listeningMc_req))) < 0) {
NSLog(@"ERROR: listenForPackets - setsockopt() drop membership failed");
//return 1; // make the method return an int instead of void and use this statement to check for errors
}
close(listeningSock);
NSLog(@"listenForPackets - Stage 5 - Complete");
}