问题
I am creating a multiplayer game using MPCF. You control a spacehip on the iPad using the iPhone.
I am experiencing various amount of lag and latency and buffering/pauses at random times and intervals and have now landed on Apples Technical Q&A NW26 paper that talks about disabled the Nagle Algorithm. Im trying it out but my program keeps crashing and I dont understand why. It seem to be that CFWriteStreamCopyProperty always return NULL.
- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)eventCode
{
switch (eventCode) {
case NSStreamEventOpenCompleted:
// Trying to get a handle to the native socket
CFSocketNativeHandle rawsock;
// This always return NULL
CFDataRef socketData = CFWriteStreamCopyProperty((__bridge CFWriteStreamRef)(stream), kCFStreamPropertySocketNativeHandle);
// And this row always crash (coz of socketData being NULL i guess)
CFDataGetBytes(socketData, CFRangeMake(0, sizeof(CFSocketNativeHandle)), (UInt8 *)&rawsock);
CFRelease(socketData);
// Code example from Apple that need a handle to the native socket, that I am trying to get above
int err;
static const int kOne = 1;
err = setsockopt(rawsock, IPPROTO_TCP, TCP_NODELAY, &kOne, sizeof(kOne));
if (err < 0) {
err = errno;
}
break;
default:
break;
}
}
Any help is appreciated.
回答1:
You assuming that stream
is an NSOutputStream
, but there could be passed NSInputStream
also.
So it crashes on that line.
Here is a sample code that can handle both scenarios and fixes a crash:
- (void)disableNaglesAlgorithmForStream:(NSStream *)stream {
CFDataRef socketData;
// Get socket data
if ([stream isKindOfClass:[NSOutputStream class]]) {
socketData = CFWriteStreamCopyProperty((__bridge CFWriteStreamRef)((NSOutputStream *)stream), kCFStreamPropertySocketNativeHandle);
} else if ([stream isKindOfClass:[NSInputStream class]]) {
socketData = CFReadStreamCopyProperty((__bridge CFReadStreamRef)((NSInputStream *)stream), kCFStreamPropertySocketNativeHandle);
}
// get a handle to the native socket
CFSocketNativeHandle rawsock;
CFDataGetBytes(socketData, CFRangeMake(0, sizeof(CFSocketNativeHandle)), (UInt8 *)&rawsock);
CFRelease(socketData);
// Disable Nagle's algorythm
// Debug info
BOOL isInput = [stream isKindOfClass:[NSInputStream class]];
NSString * streamType = isInput ? @"INPUT" : @"OUTPUT";
int err;
static const int kOne = 1;
err = setsockopt(rawsock, IPPROTO_TCP, TCP_NODELAY, &kOne, sizeof(kOne));
if (err < 0) {
err = errno;
NSLog(@"Could Not Disable Nagle for %@ stream", streamType);
} else {
NSLog(@"Nagle Is Disabled for %@ stream", streamType);
}
}
This should be called right in the case NSStreamEventOpenCompleted:
For anyone wondering why it does not compile when copy-pasted:
#import <arpa/inet.h> // for IPPROTO_TCP
#include <netinet/tcp.h> // for TCP_NODELAY
However, it does NOT help with periodical latency issues. I'm still searching for a way to prevent that.
I recorded a simple video that demonstrates the issue and I believe you are experiencing the same one: https://www.dropbox.com/s/omdqkbckph4b1y2/Multipeer%20Connectivity.mov?dl=0
EDIT: I was able to find a way to fix a periodical latency issues. It is an MCNearbyServiceAdvertiser
that causes the issues.
You need to stop advertising a peer in order to get rid of lags:
call a stopAdvertisingPeer
method on your MCNearbyServiceAdvertiser
instance right after the connection succeeded.
MCNearbyServiceAdvertiser *nearbyServiceAdvertiser;
- (void)session:(MCSession *)session peer:(MCPeerID *)peerID didChangeState:(MCSessionState)state {
switch (state) {
case MCSessionStateConnected: {
dispatch_async(dispatch_get_main_queue(), ^{
[self.nearbyServiceAdvertiser stopAdvertisingPeer];
});
...
}
...
}
BUT the delays will turn off only after 30 seconds. I don't know how to make it disappear right away.
来源:https://stackoverflow.com/questions/23810373/disable-nagles-algorithm-for-nsoutputstream