why GCDAsyncUdpSocket cannot send/receive packets after a while in broadcast mode? - ios

Question

I am using GCDAsyncUdpSocket to write a UDP socket in my app. The scenario is like this: when users click the button, it will send a broadcast packet in LAN then listen to the response, there is a server in LAN which will respond with one UDP packet. When the app receives the response, it will do something.
I set GCDAsyncUdpSocket as followings:
- (void)setupSocket
{
_udpSocket = [[GCDAsyncUdpSocket alloc] initWithDelegate:self delegateQueue:dispatch_get_main_queue()];
NSError *error = nil;
if (![_udpSocket bindToPort:18686 error:&error]) {
NSLog(#"Error binding: %#",error);
return;
}
if (![_udpSocket beginReceiving:&error]) {
NSLog(#"Error receiving: %#",error);
return;
}
if (![_udpSocket enableBroadcast:YES error:&error]) {
NSLog(#"Error enableBroadcast: %#",error);
return;
}
}
then i send Packet in button action as following:
NSString *host = #"255.255.255.255";
int port = 8585;
NSString *msg = #"Hello from iOS";
NSData *data = [msg dataUsingEncoding:NSUTF8StringEncoding];
[_udpSocket sendData:data toHost:host port:port withTimeout:-1 tag:0];
in
- (void)udpSocket:(GCDAsyncUdpSocket *)sock didReceiveData:(NSData *)data
fromAddress:(NSData *)address
withFilterContext:(id)filterContext
method i listen the port to do somethings. It works perfectly at beginning, but if you try to click the button later (about 1 hour), then it cannot send UDP packet any more.
My server in LAN will print the data received. I thought there was something wrong with send method. so i use BSD socket methods to send The data. and use GCDAsyncUdpSocket to receive the response. but the same thing happened after a while. this time i can send but cannot receive.
Am i missing something about GCDAsyncUdpSocket? why it cannot send/receive after a while? Any help would be much appreciated.

Answer 1

It may be some timeout setting. Implement the GCDAsyncUdpSocketDelegate protocol to fetch detailed information about what is going on.
The hard solution is to establish a new connection.