Question

I have a weird issue trying to use AsyncSocket. In my app I actually need synchronous sockets because I handle all communication in background myself on a different level. So I try to write wrapper around AsyncSocket class SyncSocket. Here is code:

// SyncSocket.h
#import <Foundation/Foundation.h>
#import "AsyncSocket.h"

@interface SyncSocket : NSObject <AsyncSocketDelegate> {
    AsyncSocket* _asyncSocket;
    NSTimeInterval _connectTimeout;
    NSTimeInterval _readTimeout;
    NSTimeInterval _writeTimeout;
    BOOL _waiting;
    BOOL _nsLog;
}

@property (nonatomic, assign) BOOL waiting;
@property (nonatomic, assign) BOOL nsLog;

- (id) initWithConnectTimeout: (NSTimeInterval) connectTimeout readTimeout: (NSTimeInterval) readTimeout writeTimeout: (NSTimeInterval) writeTimeout;

- (BOOL) connectToHost: (NSString*) host onPort: (UInt16) port;

@end

// SyncSocket.m
#import "SyncSocket.h"

@implementation SyncSocket
@synthesize waiting = _waiting;
@synthesize nsLog = _nsLog;

//
// Constructor/destructor
//

- (id) initWithConnectTimeout: (NSTimeInterval) connectTimeout readTimeout: (NSTimeInterval) readTimeout writeTimeout: (NSTimeInterval) writeTimeout {
    [super init];
    if (self == nil)
        return self;

    _connectTimeout = connectTimeout;
    _readTimeout = readTimeout;
    _writeTimeout = writeTimeout;
    _waiting = NO;

    _asyncSocket = [[AsyncSocket alloc] initWithDelegate: self];

    return self;
}

- (void) dealloc {
    [_asyncSocket release];
    [super dealloc];
}

- (BOOL) connectToHost: (NSString*) host onPort: (UInt16) port {
    if (self.nsLog)
        NSLog (@"connectToHost: %@ onPort: %d", host, port);

    _waiting = YES;
    NSError* err = nil;
    if (![_asyncSocket connectToHost: host
                      onPort: port
                     withTimeout: _connectTimeout
                   error: &err])
        return NO;

    while (self.waiting && [_asyncSocket isConnected] == NO) {
        [NSThread sleepForTimeInterval: 0.01];
    }


    return [_asyncSocket isConnected];
}

- (void) writeData: (NSData*) data {
    _waiting = YES;
    [_asyncSocket writeData: data withTimeout: _writeTimeout tag: 0];

    while (self.waiting) {
        [NSThread sleepForTimeInterval: 0.01];
    }
}


//
// AsyncSocket delegates
// 
- (BOOL)onSocketWillConnect:(AsyncSocket *)sock {
    if (self.nsLog)
        NSLog (@"onSocketWillConnect:");
    return YES;
}

- (void)onSocket:(AsyncSocket *)sock didWriteDataWithTag:(long)tag {
    if (self.nsLog)
        NSLog (@"didWriteDataWithTag: %d", tag);
    _waiting = NO;
}

- (void) onSocket: (AsyncSocket*) sock willDisconnectWithError: (NSError*) err {
    if (self.nsLog)
        NSLog (@"willDisconnectWithError: %d", [err code]);

    _waiting = NO;
}

- (void) onSocket: (AsyncSocket*) sock didConnectToHost: (NSString*) host port: (UInt16) port {
    if (self.nsLog)
        NSLog (@"didConnectToHost: %@ port: %d", host, port);

    _waiting = NO;
}

@end

The problem is: AsyncSocket connects to the host just fine, but my delegate didConnetToHost is never called. And if I debug AsyncSocket code I can see that even though delegate is set respondsToSelector fails. Looks like there is some strange memory violation or something but I have no idea where did I do mistake.

Any ideas? Is there a good example on how to wrap AsyncSocket to be synchronous socket?

PS: Just to be clear: XCode 3.2.5, iPhone Simulator 4.2.

Update: The reason I’m trying to wrap it with SyncSocket is because I wanted to hide all socket delegate stuff from business logic of application. I need to use socket connection in many different places and I don’t want to implement low level socket functions (like detecting state of the socket, receiving header of the message then body etc) in many different places. I want to have simple interface where I can open/send/receive and don’t worry about low level implementation. I do understand that network connectivity should be run in separate thread and that’s fine – making one background worker in the main thread is not a problem.

So I took InterfaceTest sample from AsyncSocket repository as a starting point. Removed DNS related stuff from there. Works fine. didConnect get called, everything is shiny.

I added then to the project my SyncSocket implementation to see what’s wrong with it. Project can be downloaded here: http://dl.dropbox.com/u/6402890/NetworkTest.zip – may be somebody can tell me what I’m doing wrong – I got a feeling that I’m not using threads properly in SyncSocket.

If I use in waiting loop both asyncSocket is Connected and my internal self.waiting – it gets out of that loop and didConnect is called (but AFTER the loop is finished). If I try to use only my self.waiting which is set in didConnect – didConnect never called and application hangs.

Anybody can tell me what’s wrong?

Answer 1

Found a problem. Looks like I had to change waiting loop from using:

[[NSThread sleepForTimeInterval: 0.01]

To using RunLoop:

[[NSRunLoop currentRunLoop] runUntilDate: [NSDate dateWithTimeIntervalSinceNow: 0.01]];