iOS websocket

最近在开发一个直播应用，需要用到弹幕功能，后台说要用websocket来实现，所以学习了一下

一、 RocketSocket
搜索了一下发现，用的最多的还是Facebook的RocketSocket库，虽然已经停止维护了，但是还能使用。

创建socket

- (SRWebSocket *)webSocket {
    if (!_webSocket) {
        NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:SOCKET_SERVER_URL]];
        [request setValue:[NSString getAccessTokenString] forHTTPHeaderField:@"Authorization"];
        _webSocket = [[SRWebSocket alloc] initWithURLRequest:request];
        _webSocket.delegate = self;
    }
    return _webSocket;
}

打开socket，开始连接

- (void)openWebSocket {
    if (self.webSocket.readyState == SR_OPEN) {
        return;
    }
    [self.webSocket open];
}

监听消息

- (void)subscribeNewMessage {
    NSString *sendString = [NSString stringWithFormat:@"SUBSCRIBE
destination: %@
id: %@

", SOCKET_SEND_URL(@(self.channelId)), @"sub-0"];
    NSLog(@"%@", sendString);
    NSData *data = [sendString dataUsingEncoding:NSUTF8StringEncoding];
    [self.webSocket send:data];
}

发送消息

- (void)sendMessage:(NSDictionary *)message {
    if (self.webSocket) {
        if (self.webSocket.readyState == SR_OPEN) {
            NSString *sendString = [NSString stringWithFormat:@"SEND
Authorization: %@
destination: %@

%@", [NSString getAccessTokenString], SOCKET_SEND_URL(message[@"accountId"]), [NSString getJsonStringOfDictionary:message]];
            NSLog(@"sendMessage :%@", sendString);
            NSData *data = [sendString dataUsingEncoding:NSUTF8StringEncoding];
            [self.webSocket send:data];
        }
    } else {
        [self openWebSocket];
    }
}

SRWebSocketDelegate, 代理事件

#pragma mark - SRWebSocketDelegate

- (void)webSocketDidOpen:(SRWebSocket *)webSocket {
    NSLog(@"webSocketDidOpen");
    if ([webSocket isEqual:self.webSocket]) {
        self.reopenCount = 0;
//        [self startHeartBeat];
//        [self subscribeNewMessage];
    }
}

- (void)webSocket:(SRWebSocket *)webSocket didFailWithError:(NSError *)error {
    NSLog(@"didFailWithError: %@", error);
    if ([webSocket isEqual:self.webSocket]) {
        [self reopenWebSocket];
    }
}

- (void)webSocket:(SRWebSocket *)webSocket didCloseWithCode:(NSInteger)code reason:(NSString *)reason wasClean:(BOOL)wasClean {
    NSLog(@"didCloseWithCode: %ld, %@, %d", (long)code, reason, wasClean);
    if ([webSocket isEqual:self.webSocket]) {
        [self closeWebSocket];
    }
}

- (void)webSocket:(SRWebSocket *)webSocket didReceivePong:(NSData *)pongPayload {
    NSLog(@"didReceivePong: %@", pongPayload);
    if ([webSocket isEqual:self.webSocket]) {

    }
}

- (void)webSocket:(SRWebSocket *)webSocket didReceiveMessage:(id)message {
    NSLog(@"didReceiveMessage: %@", message);
    if ([webSocket isEqual:self.webSocket]) {
        if (self.receiveMessage) {
            self.receiveMessage(message);
        }
    }
}

心跳和重连
因为封装的比较简单，代码看起来很明了，但是有些地方需要自己完善。我这里主要加了心跳和重连机制。

- (NSTimer *)heartBeatTimer {
    if (!_heartBeatTimer) {
        _heartBeatTimer = [NSTimer timerWithTimeInterval:heartBeatTimeInterval target:self selector:@selector(sendPing) userInfo:nil repeats:YES];
    }
    return _heartBeatTimer;
}

- (void)startHeartBeat {
    if (!_heartBeatTimer) {
        [[NSRunLoop currentRunLoop] addTimer:self.heartBeatTimer forMode:NSRunLoopCommonModes];
//        [[NSRunLoop currentRunLoop] run];//子线程需要手动启动runloop
    }
}

- (void)stopHeartBeat {
    if (_heartBeatTimer) {
        [self.heartBeatTimer invalidate];
        self.heartBeatTimer = nil;
    }
}

- (void)sendPing {
    if (self.webSocket.readyState == SR_OPEN) {
        [self.webSocket sendPing:nil];
    }
}

- (void)reopenWebSocket {
    [self closeWebSocket];
    if (self.reopenCount >= maxReopenCount) {
        if (self.reconnectFailed) {
            self.reconnectFailed();
        }
        return;
    }
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 2 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
        [self openWebSocket];
        self.reopenCount ++;
    });
}

二、 WebsocketStompKit
用rocketsocket写完之后，开始和后端联调，发现连接成功之后后端根本发现不了，连log都没有。对比着js中的方法，发现有用到Stomp，看源码挺简单的，只是把数据封装了一层，所以我就照着写了，在调试的时候还是不行。然后就去网上搜索iOS支持stomp协议的websocket库，就找到了这个WebsocketStompKit。

这个库封装的更好一些，用起来很方便。

创建client

- (STOMPClient *)webSocket {
    if (!_webSocket) {
        NSURL *url = [NSURL URLWithString:SOCKET_SERVER_URL];
        NSDictionary *headers = @{
            @"Authorization": [NSString getAccessTokenString],
        };
        _webSocket = [[STOMPClient alloc] initWithURL:url webSocketHeaders:headers useHeartbeat:YES];
        _webSocket.delegate = self;
    }
    return _webSocket;
}

打开socket，开始连接

- (void)openWebSocket {
    NSDictionary *headers = @{
        @"Authorization": [NSString getAccessTokenString],
    };
    [self.webSocket connectWithHeaders:headers completionHandler:^(STOMPFrame *connectedFrame, NSError *error) {
        NSLog(@"connectWithHeaders: %@---%@", connectedFrame, error);
        if (error) {//连接失败提示
            dispatch_async(dispatch_get_main_queue(), ^{
                
            });
        } else {//连接成功订阅消息
            [self subscribeNewMessage];
        }
    }];
}

订阅消息

- (void)subscribeNewMessage {
    [self.webSocket subscribeTo:[NSString stringWithFormat:@"/topic/222.%lld", self.channelId] headers:@{} messageHandler:^(STOMPMessage *message) {
        NSLog(@"receive message: %@", message);
        if (self.receiveMessage) {
            self.receiveMessage([NSString getDictionaryFromJsonString:message.body]);
        }
    }];
}

发送消息

- (void)sendMessage:(NSDictionary *)message {
    NSDictionary *headers = @{
        @"Authorization": [NSString getAccessTokenString],
    };
    [self.webSocket sendTo:SOCKET_SEND_URL(message[@"accountId"]) headers:headers body:[NSString getJsonStringOfDictionary:message]];
}

使用过程中又崩溃的情况，我这里修改了几个地方，详情请见我的Fork

比较上面的两种库，回调方式分别用来delegate和block，看起来使用delegate的方式容易对整个流程有把控，每一步都有对应的方法，写起来稍微麻烦一些，但是容易理解；使用block的方式写起来很简单，但是理解起来稍显困难，不过更容易集中注意力到事件及回调上，其他过程可忽略。我倾向于前者。

参考:
iOS WebSocket长连接
 WebSocket Demo
WebsocketStompKit使用