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