一.t-io是幹嘛的
這個框架已經開源到碼雲上面，介紹比較詳細，鏈接：https://git.oschina.net/tywo45/t-io，由於官方介紹中的入門程序客戶端和服務端都是用的java寫的，而且是用簡單的自定義TCP協議進行通信的，也有一個websocket協議的列子，感覺有點複雜，不好入門。就想着使用javascript來做客戶端，t-io做服務端，採用websocket協議搞一個helloworld。
二.WebSocket協議咋回事
首先，t-io框架簡單說就是封裝一下些個：
- 內置心跳檢測
- 內置心跳發送
- 各種便捷的綁定API
- 各種便捷的發送API
- 一行代碼擁有自動重連功能
- 各項消息統計等功能，全部一鍵內置搞定，省卻各種煩惱
所以我們收到客戶端發來的websocket協議的包，在服務端就要做對應的解包，那我們還要了解websocket包的結構和通信建立的過程：
①握手階段：
客戶端和服務器建立TCP連接之後，客戶端發送握手請求，隨後服務器發送握手響應即完成握手階段。如下：
客戶端握手請求類似如下：
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
服務器的握手響應類似如下：
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: HSmrc0sMlYUkAGmm5OPpG2HaGWk=
Sec-WebSocket-Protocol: chat
②握手成功後開始發送數據幀
這是Websocket的數據傳輸協議，聊天信息一般會按照這個協議的規則來傳輸，下圖中的一整個東西稱爲一個數據幀，數據幀的成幀和解析是處理這個協議時最麻煩的一部分了。具體這個表怎麼看可以參照
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 ... |
+---------------------------------------------------------------+
具體每一bit的意思
FIN 1bit 表示信息的最後一幀
RSV 1-3 1bit each 以後備用的 默認都爲 0
Opcode 4bit 幀類型，稍後細說
Mask 1bit 掩碼，是否加密數據，默認必須置爲1 （這裏很蛋疼）
Payload 7bit 數據的長度
Masking-key 1 or 4 bit 掩碼
Payload data (x + y) bytes 數據
Extension data x bytes 擴展數據
Application data y bytes 程序數據
三.T-io服務端編寫
整體的編寫和框架自帶的Helloworld程序模式一致，需要改變的就是encode()編碼方法和decode()解碼方法，因爲需要根據websocket協議來。
收到消息後先解碼，再判斷包的類型，交給響應類型的handler。發送消息先編碼。
①握手
decode()解碼方法：
由於客戶端收到的第一個包是握手包，所以：
if (!barrageSessionContext.isHandshaked()) // 如果還沒有握手，則先進行握手操作
{
if (BarragePacket.HANDSHAKE_BYTE == firstbyte) {
buffer.position(1 + initPosition);
return handshakePacket;
} else {
HttpRequestPacket httpRequestPacket = HttpRequestDecoder.decode(buffer);
if (httpRequestPacket == null) {
return null;
}
//交給握手包的Handler
httpRequestPacket.setType(Type.COMMAND_HANDSHAKE_REQ);
barrageSessionContext.setWebsocket(true);
return httpRequestPacket;
}
}
//握手成功後在barrageSessionContext中保存此次連接的握手情況.
boolean isWebsocket = barrageSessionContext.isWebsocket();
握手包的Handler，返回握手響應包，讓客戶端知道握手成功，可以進行數據傳輸了，：
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)
{
//發送握手響應包，交給握手響應的handler
httpResponsePacket.setType(Type.COMMAND_HANDSHAKE_RESP);
Aio.send(channelContext, httpResponsePacket);
} else
{
Aio.remove(channelContext, "不是websocket協議");
}
} 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()編碼方法:
上面在握手包的handler中，調用了send方法，發送了一個握手響應包，所以要在編碼的時候先判斷是否是握手響應包，對其編碼：
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;
}
}
握手響應包的編碼
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數據包
decode()解碼方法：
上面握手成功的時候會在BarrageSessionContext中保存握手的情況。
if (isWebsocket) // 走的websocket協議
{
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("錯誤的websocket包，body爲空");
}
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("錯誤的websocket包，body爲空");
}
BarragePacket barragePacket = new BarragePacket(Type.P2P_REQ);
if (wsBody.length > 1) {
barragePacket.setBody(wsBody);
}
return barragePacket;
} else {
throw new AioDecodeException("錯誤的websocket包，錯誤的Opcode");
}
} else {
if (BarragePacket.HEARTBEAT_BYTE == firstbyte) {
buffer.position(1 + initPosition);
return heartbeatPacket;
}
}
數據包的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;
}
}
這個收到消息後的處理是，發送收到的消息到客戶端。
encode()編碼方法:
如果不是握手響應包，走websocket包的編碼
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; //固定有一個命令碼，佔一位
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協議的服務器的處理流程大致是上面這個流程，但是代碼我只貼了關鍵部分，完整的代碼可以去我的碼雲上下載。
四.javascript客戶端編寫
<!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>
最好是下載程序下來，打上斷點，debug去跟一下，每一步包做了那些處理，變成了什麼樣子，傳輸的二進制數據轉換成字符串是甚麼樣子等等。
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此項目下載地址：https://git.oschina.net/z77z/springboot_mybatisplus
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