iOS WebSocket

WebSocket是什麼

WebSocket是用於HTML的協議，能夠在單個TCP鏈接進行全雙工通訊。不一樣於HTTP協議被動性，每次客戶端先發起request,服務端再響應respon。而WebSocket是經過TCP有一個「握手」的鏈接後，客戶端和服務端均可以向對方發送數據,相似socket的數據通訊。WebSocket解決了HTTP非持久鏈接的問題，比經過輪詢和長鏈接的方式更加高效、節省資源。

iOS WebSocket的使用

• 使用的框架：SocketRocket
• 封裝一個單例：

@interface WebSocketHelper : NSObject
+ (instancetype)helper;

//開啓鏈接
- (void)connectWithURLString:(NSString *)urlString;
//發送數據
- (void)sendData:(id)data;
//關閉鏈接
- (void)closeWebSocket;
@end


#import "WebSocketHelper.h"
#import "SocketRocket/SRWebSocket.h"

@interface WebSocketHelper ()<SRWebSocketDelegate> {
    NSTimer * _heartBeatTimer;
    NSTimeInterval _reConnectTime;
}
@property (nonatomic, strong) SRWebSocket *socket;

@end


@implementation WebSocketHelper
+ (instancetype)helper {
    static WebSocketHelper *h = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        h = [[self alloc]init];
    });
    
    return h;
}


- (void)connectWithURLString:(NSString *)urlString {
    if (!urlString.length) {
        return;
    }
    if (self.socket) {
        return;
    }
    ///後臺的websocket的地址
    NSURLRequest *urlReq = [NSURLRequest requestWithURL:[NSURL URLWithString:urlString]];
    self.socket = [[SRWebSocket alloc]initWithURLRequest:urlReq];
    self.socket.delegate = self;
    //開始鏈接
    [self.socket open];
    
}

#pragma mark - SRWebSocketDelegate
- (void)webSocketDidOpen:(SRWebSocket *)webSocket {
    NSLog(@"鏈接成功");
    _reConnectTime = 0;
    //開啓心跳 心跳是發送pong的消息 我這裏根據後臺的要求發送data給後臺
    [self creatHeartBeat];
}


///鏈接失敗
- (void)webSocket:(SRWebSocket *)webSocket didFailWithError:(NSError *)error {
    NSLog(@"鏈接失敗");
}
//被一方關閉鏈接了
- (void)webSocket:(SRWebSocket *)webSocket didCloseWithCode:(NSInteger)code reason:(NSString *)reason wasClean:(BOOL)wasClean{
    NSLog(@"鏈接斷開了");
}
///接收服務器的pong消息
- (void)webSocket:(SRWebSocket *)webSocket didReceivePong:(nullable NSData *)pongData{
     NSString *reply = [[NSString alloc] initWithData:pongData encoding:NSUTF8StringEncoding];
    NSLog(@"接收到pong消息：%@",reply);
    
}

- (void)webSocket:(SRWebSocket *)webSocket didReceiveMessage:(id)message  {
    //收到服務器發過來的數據
    NSLog(@"接收到發過來的消息%@",message);
    
}


#pragma mark - custom methods


- (void)closeWebSocket {
    if (self.socket){
        //斷開鏈接
        [self.socket close];
        self.socket = nil;
        //斷開鏈接時銷燬心跳
        [self cancelHeartBeat];
    }
}

//重連,當發現客戶端和服務端斷開鏈接時發起重連
- (void)reConnect
{
    [self closeWebSocket];
    //超過一分鐘就再也不重連 因此只會重連5次 2^5 = 64
    if (_reConnectTime > 64) {
        return;
    }
    
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(_reConnectTime * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [self.socket open];
        NSLog(@"重連");
    });
    
    //重連時間2的指數級增加
    if (_reConnectTime == 0) {
        _reConnectTime = 2;
    }else{
        _reConnectTime *= 2;
    }
}

//初始化心跳
- (void)creatHeartBeat
{
    dispatch_async(dispatch_get_main_queue(), ^{
        [self cancelHeartBeat];
        __weak typeof(self) weakSelf = self;
        //心跳設置爲3分鐘，NAT超時通常爲5分鐘
        self->_heartBeatTimer = [NSTimer scheduledTimerWithTimeInterval:3*60 repeats:YES block:^(NSTimer * _Nonnull timer) {
            NSLog(@"heart");
            //發送心跳
            [weakSelf sendData:@"heart"];
        }];
        [[NSRunLoop currentRunLoop]addTimer:self -> _heartBeatTimer forMode:NSRunLoopCommonModes];
    });
    
  
}

//取消心跳
- (void)cancelHeartBeat

{
    
    dispatch_async(dispatch_get_main_queue(), ^{
        if (self->_heartBeatTimer) {
            [self->_heartBeatTimer invalidate];
            self->_heartBeatTimer = nil;
        }
    });
}
///發送數據
- (void)sendData:(id)data {
    
    dispatch_queue_t queue =  dispatch_queue_create("send.queue", NULL);
    __weak typeof(self) weakSelf = self;
    dispatch_async(queue, ^{
        if (weakSelf.socket != nil) {
            // 只有 SR_OPEN 開啓狀態才能調 send 方法，否則要崩
            if (weakSelf.socket.readyState == SR_OPEN) {
                NSError *error = nil;
                [weakSelf.socket sendData:data error:&error];    // 發送數據
                
            } else if (weakSelf.socket.readyState == SR_CONNECTING) {
                NSLog(@"正在鏈接中");
                [self reConnect];
                
            } else if (weakSelf.socket.readyState == SR_CLOSING || weakSelf.socket.readyState == SR_CLOSED) {
                // websocket 斷開了，調用 reConnect 方法重連
                [self reConnect];
            }
        } else {
            NSLog(@"沒網絡，發送失敗");
        }
    });
}


@end

複製代碼

注意：調用的sendPing、sendData方法以前，必須判斷當前scoket是否鏈接，若是不是鏈接狀態，不然程序會crash。

參考資料

www.jianshu.com/p/821b77755…