Websocket协议的原理和实现（2）(2)

读取后websocket ping，根据此数据帧的类型进行不同的回调

private void decodeFrames(ByteBuffer socketBuffer) {
    try {
        List frames = this.draft.translateFrame(socketBuffer);//读取二进制流
        for (Framedata f : frames) {
            if (DEBUG)
                System.out.println("matched frame: " + f);
            Framedata.Opcode curop = f.getOpcode();
            boolean fin = f.isFin();
            if (curop == Framedata.Opcode.CLOSING) {  //关闭帧
                int code = 1005;
                String reason = "";
                if ((f instanceof CloseFrame)) {
                    CloseFrame cf = (CloseFrame) f;
                    code = cf.getCloseCode();
                    reason = cf.getMessage();
                }
                if (this.readystate == WebSocket.READYSTATE.CLOSING) {
                    closeConnection(code, reason, true);
                } else if (this.draft.getCloseHandshakeType() == Draft.CloseHandshakeType.TWOWAY)
                    close(code, reason, true);
                else {
                    flushAndClose(code, reason, false);
                }
            } else if (curop == Framedata.Opcode.PING) {  //Ping
                this.wsl.onWebsocketPing(this, f);
            } else if (curop == Framedata.Opcode.PONG) {    //Pong
                this.wsl.onWebsocketPong(this, f);
            } else if ((!fin) || (curop == Framedata.Opcode.CONTINUOUS)) {    //分片消息
                if (curop != Framedata.Opcode.CONTINUOUS) {
                    if (this.current_continuous_frame_opcode != null)
                        throw new InvalidDataException(1002, "Previous continuous frame sequence not completed.");
                    this.current_continuous_frame_opcode = curop;
                } else if (fin) {
                    if (this.current_continuous_frame_opcode == null)
                        throw new InvalidDataException(1002, "Continuous frame sequence was not started.");
                    this.current_continuous_frame_opcode = null;
                } else if (this.current_continuous_frame_opcode == null) {
                    throw new InvalidDataException(1002, "Continuous frame sequence was not started.");
                }
                try {
                    this.wsl.onWebsocketMessageFragment(this, f);
                } catch (RuntimeException e) {
                    this.wsl.onWebsocketError(this, e);
                }
            } else {  //普通消息
                if (this.current_continuous_frame_opcode != null)
                    throw new InvalidDataException(1002, "Continuous frame sequence not completed.");
                if (curop == Framedata.Opcode.TEXT)   //文本消息
                    try {
                        this.wsl.onWebsocketMessage(this, Charsetfunctions.stringUtf8(f.getPayloadData()));
                    } catch (RuntimeException e) {
                        this.wsl.onWebsocketError(this, e);
                    }
                else if (curop == Framedata.Opcode.BINARY)    //二进制消息
                    try {
                        this.wsl.onWebsocketMessage(this, f.getPayloadData());
                    } catch (RuntimeException e) {
                        this.wsl.onWebsocketError(this, e);
                    }
                else
                    throw new InvalidDataException(1002, "non control or continious frame expected");
            }
        }
    } catch (InvalidDataException e1) {
        this.wsl.onWebsocketError(this, e1);
        close(e1);
        return;
    }
}

现在讨论控制帧的处理. WebSocket控制框架有三种类型: 关闭，乒乓和乒乓. 关闭框很容易理解. 如果客户端收到连接，则将其关闭. 客户端还可以向服务器发送关闭帧. Ping和Pong是websocket的心跳. 它们用于确保客户端. 通常，只有服务器发送ping到客户端，客户端发送Pong进行响应，表明它仍处于联机状态.

让我们看看Nathan Rajlich的Java Websocket代码. 客户端对Ping的处理非常简单. 将收到的Ping帧更改为操作码类型，然后将其发送回服务器. 您可以看到客户端处理服务器发送的Pong回调的方法为空.

public void onWebsocketPing(WebSocket conn, Framedata f) {
    FramedataImpl1 resp = new FramedataImpl1(f);
    resp.setOptcode(Framedata.Opcode.PONG);
    conn.sendFrame(resp);
}
public void onWebsocketPong(WebSocket conn, Framedata f) {
}

本文暂时是本文，下一篇是关于Websocket客户端和Websocket服务器的实现

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