即时通讯框架T-io之WebSocket协议再之HelloWorld

一.t-io是干嘛的

这个框架已经开源到码云上面，介绍比较详细，链接：https://git.oschina.net/tywo45/t-io，由于官方介绍中的入门程序客户端和服务端都是用的java写的，而且是用简单的自定义TCP协议进行通信的，也有一个websocket协议的列子，感觉有点复杂，不好入门。就想着使用javascript来做客户端，t-io做服务端，采用websocket协议搞一个helloworld。

二.WebSocket协议咋回事

首先，t-io框架简单说就是封装一下些个：

内置心跳检测
内置心跳发送
各种便捷的绑定API
各种便捷的发送API
一行代码拥有自动重连功能
各项消息统计等功能，全部一键内置搞定，省却各种烦恼

所以我们收到客户端发来的websocket协议的包，在服务端就要做对应的解包，那我们还要了解websocket包的结构和通信建立的过程：

①握手阶段：

客户端和服务器建立TCP连接之后，客户端发送握手请求，随后服务器发送握手响应即完成握手阶段。如下：

客户端握手请求类似如下：

GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13
Origin: http://example.com

服务器的握手响应类似如下：

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: HSmrc0sMlYUkAGmm5OPpG2HaGWk=
Sec-WebSocket-Protocol: chat

②握手成功后开始发送数据帧

这是Websocket的数据传输协议，聊天信息一般会按照这个协议的规则来传输，下图中的一整个东西称为一个数据帧，数据帧的成帧和解析是处理这个协议时最麻烦的一部分了。具体这个表怎么看可以参照

0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-------+-+-------------+-------------------------------+
 |F|R|R|R| opcode|M| Payload len |    Extended payload length    |
 |I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
 |N|V|V|V|       |S|             |   (if payload len==126/127)   |
 | |1|2|3|       |K|             |                               |
 +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
 |     Extended payload length continued, if payload len == 127  |
 + - - - - - - - - - - - - - - - +-------------------------------+
 |                               |Masking-key, if MASK set to 1  |
 +-------------------------------+-------------------------------+
 | Masking-key (continued)       |          Payload Data         |
 +-------------------------------- - - - - - - - - - - - - - - - +
 :                     Payload Data continued ...                :
 + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
 |                     Payload Data continued ...                |
 +---------------------------------------------------------------+
 具体每一bit的意思
FIN      1bit 表示信息的最后一帧
RSV 1-3  1bit each 以后备用的 默认都为 0
Opcode   4bit 帧类型，稍后细说
Mask     1bit 掩码，是否加密数据，默认必须置为1 （这里很蛋疼）
Payload  7bit 数据的长度
Masking-key      1 or 4 bit 掩码
Payload data     (x + y) bytes 数据
Extension data   x bytes  扩展数据
Application data y bytes  程序数据

三.T-io服务端编写

整体的编写和框架自带的Helloworld程序模式一致，需要改变的就是encode()编码方法和decode()解码方法，因为需要根据websocket协议来。

收到消息后先解码，再判断包的类型，交给响应类型的handler。发送消息先编码。

①握手

decode()解码方法：

由于客户端收到的第一个包是握手包，所以：

if (!barrageSessionContext.isHandshaked()) // 如果还没有握手，则先进行握手操作
{
	if (BarragePacket.HANDSHAKE_BYTE == firstbyte) {
		buffer.position(1 + initPosition);
		return handshakePacket;
	} else {
		HttpRequestPacket httpRequestPacket = HttpRequestDecoder.decode(buffer);
		if (httpRequestPacket == null) {
			return null;
		}
		//交给握手包的Handler
		httpRequestPacket.setType(Type.COMMAND_HANDSHAKE_REQ);
		barrageSessionContext.setWebsocket(true);
		return httpRequestPacket;
	}
}
//握手成功后在barrageSessionContext中保存此次连接的握手情况.
boolean isWebsocket = barrageSessionContext.isWebsocket();

握手包的Handler，返回握手响应包，让客户端知道握手成功，可以进行数据传输了，：

public class HandshakeReqHandler implements BarrageHandlerIntf<HandshakeBody> {
	private BarragePacket handshakeRespPacket = new BarragePacket(Type.COMMAND_HANDSHAKE_RESP);
	
	@Override
	public Object handler(
			BarragePacket packet,
			String body,
			ChannelContext<BarrageSessionContext, BarragePacket, Object> channelContext)
			throws Exception {
		BarrageSessionContext barrageSessionContext = channelContext.getSessionContext();
		barrageSessionContext.setHandshaked(true);
		boolean isWebsocket = barrageSessionContext.isWebsocket();
		if (isWebsocket)
		{
			HttpRequestPacket httpRequestPacket = (HttpRequestPacket) packet;
			HttpResponsePacket httpResponsePacket = updateWebSocketProtocol(httpRequestPacket);
			if (httpResponsePacket != null)
			{
				//发送握手响应包，交给握手响应的handler
				httpResponsePacket.setType(Type.COMMAND_HANDSHAKE_RESP);
				Aio.send(channelContext, httpResponsePacket);
			} else
			{
				Aio.remove(channelContext, "不是websocket协议");
			}
		} else
		{
			Aio.send(channelContext, handshakeRespPacket);
		}
		return null;
	}
	
	public HttpResponsePacket updateWebSocketProtocol(HttpRequestPacket httpRequestPacket)
	{
		Map<String, String> headers = httpRequestPacket.getHeaders();
		String Sec_WebSocket_Key = headers.get("Sec-WebSocket-Key");
		if (StringUtils.isNotBlank(Sec_WebSocket_Key))
		{
			String Sec_WebSocket_Key_Magic = Sec_WebSocket_Key + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
			byte[] key_array = SHA1Util.SHA1(Sec_WebSocket_Key_Magic);
			String acceptKey = BASE64Util.byteArrayToBase64(key_array);
			HttpResponsePacket httpResponsePacket = new HttpResponsePacket();
			HttpResponseStatus httpResponseStatus = HttpResponseStatus.C101;
			httpResponsePacket.setHttpResponseStatus(httpResponseStatus);
			Map<String, String> respHeaders = new HashMap<>();
			respHeaders.put("Connection", "Upgrade");
			respHeaders.put("Upgrade", "WebSocket");
			respHeaders.put("Sec-WebSocket-Accept", acceptKey);
			httpResponsePacket.setHeaders(respHeaders);
			return httpResponsePacket;
		}
		return null;
	}
}

encode()编码方法:

上面在握手包的handler中，调用了send方法，发送了一个握手响应包，所以要在编码的时候先判断是否是握手响应包，对其编码：

if (packet.getType() == Type.COMMAND_HANDSHAKE_RESP) {
	if (isWebsocket) {
		return HttpResponseEncoder.encode((HttpResponsePacket) packet, groupContext, channelContext);
	} else {
		ByteBuffer buffer = ByteBuffer.allocate(1);
		buffer.put(BarragePacket.HANDSHAKE_BYTE);
		return buffer;
	}
}

握手响应包的编码

public static ByteBuffer encode(HttpResponsePacket httpResponsePacket, GroupContext<BarrageSessionContext, BarragePacket, Object> groupContext, ChannelContext<BarrageSessionContext, BarragePacket, Object> channelContext)
	{
		int bodyLength = 0;
		byte[] httpResponseBody = httpResponsePacket.getHttpResponseBody();
		if (httpResponseBody != null)
		{
			bodyLength = httpResponseBody.length;
		}
		StringBuilder sb = new StringBuilder(128);
		HttpResponseStatus httpResponseStatus = httpResponsePacket.getHttpResponseStatus();
		//		httpResponseStatus.get
		sb.append("HTTP/1.1 ").append(httpResponseStatus.getStatus()).append(" ").append(httpResponseStatus.getDescription()).append("\r\n");
		Map<String, String> headers = httpResponsePacket.getHeaders();
		if (headers != null && headers.size() > 0)
		{
			headers.put("Content-Length", bodyLength + "");
			Set<Entry<String, String>> set = headers.entrySet();
			for (Entry<String, String> entry : set)
			{
				sb.append(entry.getKey()).append(": ").append(entry.getValue()).append("\r\n");
			}
		}
		sb.append("\r\n");
		byte[] headerBytes = null;
		try
		{
			headerBytes = sb.toString().getBytes("utf-8");
		} catch (Exception e)
		{
			throw new RuntimeException(e);
		}
		ByteBuffer buffer = ByteBuffer.allocate(headerBytes.length + bodyLength);
		buffer.put(headerBytes);
		if (bodyLength > 0)
		{
			buffer.put(httpResponseBody);
		}
		return buffer;
	}

②数据包

decode()解码方法：

上面握手成功的时候会在BarrageSessionContext中保存握手的情况。

if (isWebsocket) // 走的websocket协议
{
	WebsocketPacket websocketPacket = WebsocketDecoder.decode(buffer, channelContext);
	if (websocketPacket == null) {
		return null;
	}
	Opcode opcode = websocketPacket.getWsOpcode();
	if (opcode == Opcode.BINARY) {
		byte[] wsBody = websocketPacket.getWsBody();
		if (wsBody == null || wsBody.length == 0) {
			throw new AioDecodeException("错误的websocket包，body为空");
		}
		BarragePacket barragePacket = new BarragePacket(Type.COMMAND_HANDSHAKE_RESP);
		if (wsBody.length > 1) {
			byte[] dst = new byte[wsBody.length - 1];
			System.arraycopy(wsBody, 1, dst, 0, dst.length);
			barragePacket.setBody(dst);
		}
		return barragePacket;
	} else if (opcode == Opcode.PING || opcode == Opcode.PONG) {
		return heartbeatPacket;
	} else if (opcode == Opcode.CLOSE) {
		BarragePacket barragePacket = new BarragePacket(Type.COMMAND_CLOSE_REQ);
		return barragePacket;
	} else if (opcode == Opcode.TEXT) {
		byte[] wsBody = websocketPacket.getWsBody();
		if (wsBody == null || wsBody.length == 0) {
			throw new AioDecodeException("错误的websocket包，body为空");
		}
		BarragePacket barragePacket = new BarragePacket(Type.P2P_REQ);
		if (wsBody.length > 1) {
			barragePacket.setBody(wsBody);
		}
		return barragePacket;
	} else {
		throw new AioDecodeException("错误的websocket包，错误的Opcode");
	}
} else {
	if (BarragePacket.HEARTBEAT_BYTE == firstbyte) {
		buffer.position(1 + initPosition);
		return heartbeatPacket;
	}
}

数据包的handler：

public class P2PReqHandler implements BarrageHandlerIntf<P2PReqBody>{
	@Override
	public Object handler(
			BarragePacket packet,
			String jsonStr,
			ChannelContext<BarrageSessionContext, BarragePacket, Object> channelContext)
			throws Exception {
		System.out.println(jsonStr);
		BarragePacket barragePacket = new BarragePacket(Type.P2P_REQ);
		barragePacket.setBody(("收到了你的消息，你的消息是:" + jsonStr).getBytes(BarragePacket.CHARSET));
		Aio.send(channelContext, barragePacket);
		return null;
	}
}

这个收到消息后的处理是，发送收到的消息到客户端。

encode()编码方法:

如果不是握手响应包，走websocket包的编码
if (isWebsocket) {
	return WebsocketEncoder.encode(packet, groupContext, channelContext);
}

public static ByteBuffer encode(BarragePacket barragePacket, GroupContext<BarrageSessionContext, BarragePacket, Object> groupContext,
			ChannelContext<BarrageSessionContext, BarragePacket, Object> channelContext)
{
	byte[] websocketHeader;
	byte[] imBody = barragePacket.getBody();
	int wsBodyLength = 1; //固定有一个命令码，占一位
	if (imBody != null)
	{
		wsBodyLength += imBody.length;
	}
	byte header0 = (byte) (0x8f & (Opcode.BINARY.getCode() | 0xf0));
	if (wsBodyLength < 126)
	{
		websocketHeader = new byte[2];
		websocketHeader[0] = header0;
		websocketHeader[1] = (byte) wsBodyLength;
	} else if (wsBodyLength < ((1 << 16) - 1))
	{
		websocketHeader = new byte[4];
		websocketHeader[0] = header0;
		websocketHeader[1] = 126;
		websocketHeader[3] = (byte) (wsBodyLength & 0xff);
		websocketHeader[2] = (byte) ((wsBodyLength >> 8) & 0x80);
	} else
	{
		websocketHeader = new byte[6];
		websocketHeader[0] = header0;
		websocketHeader[1] = 127;
		int2Byte(websocketHeader, wsBodyLength, 2);
	}
	ByteBuffer buf = ByteBuffer.allocate(websocketHeader.length + wsBodyLength);
	buf.put(websocketHeader);
	buf.put(barragePacket.getType());
	if (imBody != null)
	{
		buf.put(imBody);
	}
	return buf;
}
public static void int2Byte(byte[] bytes, int value, int offset)
{
	checkLength(bytes, 4, offset);
	bytes[offset + 3] = (byte) ((value & 0xff));
	bytes[offset + 2] = (byte) ((value >> 8 * 1) & 0xff);
	bytes[offset + 1] = (byte) ((value >> 8 * 2) & 0xff);
	bytes[offset + 0] = (byte) ((value >> 8 * 3));
}
private static void checkLength(byte[] bytes, int length, int offset)
{
	if (bytes == null)
	{
		throw new IllegalArgumentException("null");
	}
	if (offset < 0)
	{
		throw new IllegalArgumentException("invalidate offset " + offset);
	}
	if (bytes.length - offset < length)
	{
		throw new IllegalArgumentException("invalidate length " + bytes.length);
	}
}

websocket协议的服务器的处理流程大致是上面这个流程，但是代码我只贴了关键部分，完整的代码可以去我的码云上下载。

四.javascript客户端编写

<!DOCTYPE html>
<html>
<head>
<title>Testing websockets</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
  <div>
    <input type="submit" value="Start" onclick="start()" />
  </div>
  <div id="messages"></div>
  <script type="text/javascript">
    var webSocket = 
      new WebSocket('ws://localhost:5678');
    webSocket.onerror = function(event) {
      onError(event)
    };
    webSocket.onopen = function(event) {
      onOpen(event)
    };
    webSocket.onmessage = function(event) {
      onMessage(event)
    };
    function onMessage(event) {
		var blob = event.data;
		var reader = new FileReader();
		reader.readAsText(blob, 'utf-8');
		reader.onload = function (e) {
			document.getElementById('messages').innerHTML 
			+= '<br />' + reader.result;
		}
    }
    function onOpen(event) {
      document.getElementById('messages').innerHTML 
        = 'Connection established';
    }
    function onError(event) {
      alert(event.data);
    }
    function start() {
      webSocket.send('hellohellohellohellohellohellohellohellohe');
    }
  </script>
</body>
</html>

最好是下载程序下来，打上断点，debug去跟一下，每一步包做了那些处理，变成了什么样子，传输的二进制数据转换成字符串是甚么样子等等。

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个人博客：http://z77z.oschina.io/

此项目下载地址：https://git.oschina.net/z77z/springboot_mybatisplus

即时通讯框架T-io之WebSocket协议再之HelloWorld

一.t-io是干嘛的

二.WebSocket协议咋回事

三.T-io服务端编写

四.javascript客户端编写

我只要一角钱~ ~