I've added a simple category on socket.IO-objc to use block callbacks instead of delegate callbacks.

SocketTesterARC.xcodeproj/project.pbxproj

@@ -38,6 +38,7 @@
 		4ADCCBF315790FDF0022990C /* SystemConfiguration.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 4ADCCBF215790FDF0022990C /* SystemConfiguration.framework */; };
 		4ADCCD4D157915F00022990C /* SocketIO.m in Sources */ = {isa = PBXBuildFile; fileRef = 4ADCCBC715790DEC0022990C /* SocketIO.m */; };
 		C9E391A215E2A1B00004693A /* SocketIOJSONSerialization.m in Sources */ = {isa = PBXBuildFile; fileRef = C9E391A115E2A1B00004693A /* SocketIOJSONSerialization.m */; };
+		FA4408951849FDCC006FA1EA /* SocketIO+Blocks.m in Sources */ = {isa = PBXBuildFile; fileRef = FA4408941849FDCC006FA1EA /* SocketIO+Blocks.m */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
@@ -98,6 +99,8 @@
 		4ADCCBF215790FDF0022990C /* SystemConfiguration.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = SystemConfiguration.framework; path = System/Library/Frameworks/SystemConfiguration.framework; sourceTree = SDKROOT; };
 		C9E391A015E2A1B00004693A /* SocketIOJSONSerialization.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = SocketIOJSONSerialization.h; sourceTree = SOURCE_ROOT; };
 		C9E391A115E2A1B00004693A /* SocketIOJSONSerialization.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = SocketIOJSONSerialization.m; sourceTree = SOURCE_ROOT; };
+		FA4408931849FDCC006FA1EA /* SocketIO+Blocks.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "SocketIO+Blocks.h"; sourceTree = "<group>"; };
+		FA4408941849FDCC006FA1EA /* SocketIO+Blocks.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "SocketIO+Blocks.m"; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -197,6 +200,7 @@
 		4ADCCBA715790D760022990C /* SocketTesterARC */ = {
 			isa = PBXGroup;
 			children = (
+				FA4408921849FDC1006FA1EA /* SocketIOBlocks */,
 				4A4453791589EE7D00B44ABB /* SocketRocket */,
 				4A4453781589EE6300B44ABB /* SBJson */,
 				4ADCCBB015790D760022990C /* AppDelegate.h */,
@@ -231,6 +235,15 @@
 			name = "Supporting Files";
 			sourceTree = "<group>";
 		};
+		FA4408921849FDC1006FA1EA /* SocketIOBlocks */ = {
+			isa = PBXGroup;
+			children = (
+				FA4408931849FDCC006FA1EA /* SocketIO+Blocks.h */,
+				FA4408941849FDCC006FA1EA /* SocketIO+Blocks.m */,
+			);
+			path = SocketIOBlocks;
+			sourceTree = "<group>";
+		};
 /* End PBXGroup section */
 
 /* Begin PBXNativeTarget section */
@@ -302,6 +315,7 @@
 				4A4453821589EE9100B44ABB /* NSData+SRB64Additions.m in Sources */,
 				4A4453831589EE9100B44ABB /* SRWebSocket.m in Sources */,
 				C9E391A215E2A1B00004693A /* SocketIOJSONSerialization.m in Sources */,
+				FA4408951849FDCC006FA1EA /* SocketIO+Blocks.m in Sources */,
 				4AD96DF41680853E00D9E42D /* SocketIOPacket.m in Sources */,
 				4AD96DF816808B7900D9E42D /* SocketIOTransportWebsocket.m in Sources */,
 				4AD96DFC16822DE300D9E42D /* SocketIOTransportXHR.m in Sources */,

SocketTesterARC/SocketIOBlocks/SocketIO+Blocks.h

@@ -0,0 +1,32 @@
+//
+//  SocketIO+Blocks.h
+//
+//  Created by Anton Domashnev on 06.11.13.
+//  Copyright (c) 2013 Anton Domashnev. All rights reserved.
+//
+
+#import "SocketIO.h"
+
+@interface SocketIOBlocksDelegate : NSObject<SocketIODelegate>
+
+@end
+
+@interface SocketIO (Blocks)
+
+- (void)connectToHost:(NSString *)host onPort:(NSInteger)port withCallback:(void (^)(SocketIO *, NSError *))callback;
+- (void)connectToHost:(NSString *)host onPort:(NSInteger)port withParams:(NSDictionary *)params withCallback:(void (^)(SocketIO *, NSError *))callback;
+- (void)connectToHost:(NSString *)host onPort:(NSInteger)port withParams:(NSDictionary *)params withNamespace:(NSString *)endpoint withCallback:(void (^)(SocketIO *, NSError *))callback;
+
+- (void)addErrorHandler:(void (^)(SocketIO *, NSError *))handler forKey:(NSString *)key;
+- (void)removeErrorHandlerForKey:(NSString *)key;
+
+- (void)addMessageHandler:(void (^)(SocketIO *, SocketIOPacket *))handler forKey:(NSString *)key;
+- (void)removeMessageHandlerForKey:(NSString *)key;
+
+- (void)addJSONHandler:(void (^)(SocketIO *, SocketIOPacket *))handler forKey:(NSString *)key;
+- (void)removeJSONHandlerForKey:(NSString *)key;
+
+- (void)addEventHandler:(void (^)(SocketIO *, SocketIOPacket *))handler forKey:(NSString *)key;
+- (void)removeEventHandlerForKey:(NSString *)key;
+
+@end

SocketTesterARC/SocketIOBlocks/SocketIO+Blocks.m

@@ -0,0 +1,210 @@
+//
+//  SocketIO+Blocks.m
+//
+//  Created by Anton Domashnev on 06.11.13.
+//  Copyright (c) 2013 Anton Domashnev. All rights reserved.
+//
+
+#import "SocketIO+Blocks.h"
+
+#import <objc/runtime.h>
+
+#define SocketIOBlockSafeRun(block, ...) block ? block(__VA_ARGS__) : nil
+
+@interface SocketIOBlocksDelegate()<SocketIODelegate>
+
+@property (nonatomic, copy) void (^onStart)(SocketIO *, NSError *);
+
+@property (nonatomic, strong) NSMutableDictionary *onErrorBlocksDictionary;
+@property (nonatomic, strong) NSMutableDictionary *onMessageBlocksDictionary;
+@property (nonatomic, strong) NSMutableDictionary *onJSONBlocksDictionary;
+@property (nonatomic, strong) NSMutableDictionary *onEventBlocksDictionary;
+
+@end
+
+@implementation SocketIOBlocksDelegate
+
+- (instancetype)init{
+
+    if(self = [super init]){
+
+        self.onErrorBlocksDictionary = [NSMutableDictionary new];
+        self.onMessageBlocksDictionary = [NSMutableDictionary new];
+        self.onJSONBlocksDictionary = [NSMutableDictionary new];
+        self.onEventBlocksDictionary = [NSMutableDictionary new];
+    }
+
+    return self;
+}
+
+- (void)socketIODidConnect:(SocketIO *)socket{
+
+    SocketIOBlockSafeRun(self.onStart, socket, nil);
+}
+
+- (void)socketIODidDisconnect:(SocketIO *)socket disconnectedWithError:(NSError *)error{
+
+    SocketIOBlockSafeRun(self.onStart, socket, error);
+}
+
+- (void) socketIO:(SocketIO *)socket didReceiveMessage:(SocketIOPacket *)packet{
+
+    [self.onMessageBlocksDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
+        void(^block)(SocketIO *, SocketIOPacket *) = obj;
+        SocketIOBlockSafeRun(block, socket, packet);
+    }];
+}
+
+- (void) socketIO:(SocketIO *)socket didReceiveJSON:(SocketIOPacket *)packet{
+
+    [self.onJSONBlocksDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
+        void(^block)(SocketIO *, SocketIOPacket *) = obj;
+        SocketIOBlockSafeRun(block, socket, packet);
+    }];
+}
+
+- (void) socketIO:(SocketIO *)socket didReceiveEvent:(SocketIOPacket *)packet{
+
+    [self.onEventBlocksDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
+        void(^block)(SocketIO *, SocketIOPacket *) = obj;
+        SocketIOBlockSafeRun(block, socket, packet);
+    }];
+}
+
+- (void) socketIO:(SocketIO *)socket onError:(NSError *)error{
+
+    [self.onErrorBlocksDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
+        void(^block)(SocketIO *, NSError *) = obj;
+        SocketIOBlockSafeRun(block, socket ,error);
+    }];
+}
+
+@end
+
+@interface SocketIO(Private)
+
+@property (nonatomic, strong) SocketIOBlocksDelegate *blocksDelegate;
+
+@end
+
+@implementation SocketIO (Blocks)
+
+- (void)setBlocksDelegate:(SocketIOBlocksDelegate *)blocksDelegate{
+
+    objc_setAssociatedObject(self, @"SocketIOBlocksDelegate", blocksDelegate, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+}
+
+- (SocketIOBlocksDelegate *)blocksDelegate{
+
+    return objc_getAssociatedObject(self, @"SocketIOBlocksDelegate");
+}
+
+#pragma mark - Helpers
+
+- (void)setBlocksDelegateIfNeeded{
+
+    if(!self.delegate || ![self.delegate isKindOfClass:[SocketIOBlocksDelegate class]]){
+        self.blocksDelegate = [SocketIOBlocksDelegate new];
+        self.delegate = self.blocksDelegate;
+    }
+}
+
+- (void)connectToHost:(NSString *)host onPort:(NSInteger)port withCallback:(void (^)(SocketIO *, NSError *))callback{
+
+    [self connectToHost:host onPort:port withParams:nil withCallback:callback];
+}
+
+- (void)connectToHost:(NSString *)host onPort:(NSInteger)port withParams:(NSDictionary *)params withCallback:(void (^)(SocketIO *, NSError *))callback{
+
+    [self connectToHost:host onPort:port withParams:params withNamespace:nil withCallback:callback];
+}
+
+- (void)connectToHost:(NSString *)host onPort:(NSInteger)port withParams:(NSDictionary *)params withNamespace:(NSString *)endpoint withCallback:(void (^)(SocketIO *, NSError *))callback{
+
+    [self setBlocksDelegateIfNeeded];
+    ((SocketIOBlocksDelegate *)self.delegate).onStart = callback;
+
+    [self connectToHost:host onPort:port withParams:params withNamespace:endpoint];
+}
+
+#pragma mark - @selector(socketIO:onError:)
+
+- (void)addErrorHandler:(void (^)(SocketIO *, NSError *))handler forKey:(NSString *)key{
+
+    NSParameterAssert(key);
+    NSParameterAssert(handler);
+
+    [self setBlocksDelegateIfNeeded];
+    ((SocketIOBlocksDelegate *)self.delegate).onErrorBlocksDictionary[key] = handler;
+}
+
+- (void)removeErrorHandlerForKey:(NSString *)key{
+
+    NSParameterAssert(key);
+
+    if(self.delegate){
+        [((SocketIOBlocksDelegate *)self.delegate).onErrorBlocksDictionary removeObjectForKey:key];
+    }
+}
+
+#pragma mark - @selector(socketIO:didReceiveMessage:)
+
+- (void)addMessageHandler:(void (^)(SocketIO *, SocketIOPacket *))handler forKey:(NSString *)key{
+
+    NSParameterAssert(key);
+    NSParameterAssert(handler);
+
+    [self setBlocksDelegateIfNeeded];
+    ((SocketIOBlocksDelegate *)self.delegate).onMessageBlocksDictionary[key] = handler;
+}
+
+- (void)removeMessageHandlerForKey:(NSString *)key{
+
+    NSParameterAssert(key);
+
+    if(self.delegate){
+        [((SocketIOBlocksDelegate *)self.delegate).onMessageBlocksDictionary removeObjectForKey:key];
+    }
+}
+
+#pragma mark - @selector(socketIO:didReceiveJSON:)
+
+- (void)addJSONHandler:(void (^)(SocketIO *, SocketIOPacket *))handler forKey:(NSString *)key{
+
+    NSParameterAssert(key);
+    NSParameterAssert(handler);
+
+    [self setBlocksDelegateIfNeeded];
+    ((SocketIOBlocksDelegate *)self.delegate).onJSONBlocksDictionary[key] = handler;
+}
+
+- (void)removeJSONHandlerForKey:(NSString *)key{
+
+    NSParameterAssert(key);
+
+    if(self.delegate){
+        [((SocketIOBlocksDelegate *)self.delegate).onJSONBlocksDictionary removeObjectForKey:key];
+    }
+}
+
+#pragma mark - @selector(socketIO:didReceiveEvent:)
+
+- (void)addEventHandler:(void (^)(SocketIO *, SocketIOPacket *))handler forKey:(NSString *)key{
+
+    NSParameterAssert(key);
+    NSParameterAssert(handler);
+
+    [self setBlocksDelegateIfNeeded];
+    ((SocketIOBlocksDelegate *)self.delegate).onEventBlocksDictionary[key] = handler;
+}
+
+- (void)removeEventHandlerForKey:(NSString *)key{
+
+    NSParameterAssert(key);
+
+    if(self.delegate){
+        [((SocketIOBlocksDelegate *)self.delegate).onEventBlocksDictionary removeObjectForKey:key];
+    }
+}
+
+@end