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上一篇说到收到握手响应后的packet.type=open。接着是onHandshake（）
Socket.prototype.onHandshake = function (data) {
this.emit(‘handshake‘, data);
this.id = data.sid;
this.transport.query.sid = data.sid;
this.upgrades = this.filterUpgrades(data.upgrades);
this.pingInterval = data.pingInterval;
this.pingTimeout = data.pingTimeout;
this.onOpen();
// In case open handler closes socket
if (‘closed‘ == this.readyState) return;
this.setPing();
// Prolong liveness of socket on heartbeat
this.removeListener(‘heartbeat‘, this.onHeartbeat);
this.on(‘heartbeat‘, this.onHeartbeat);
};
Socket.prototype.onOpen = function () {
debug(‘socket open‘);
this.readyState = ‘open‘;
this.emit(‘open‘);
this.flush();
};
Socket.prototype.flush = function () {
if (‘closed‘ != this.readyState && this.transport.writable &&
!this.upgrading && this.writeBuffer.length) {
....... this.transport.send(this.writeBuffer);
}
};
writeBuffer里面没有内容，不会走里面。
Polling.prototype.onData = function(data){
.....
// decode payload
parser.decodePayload(data, this.socket.binaryType, callback);
// if an event did not trigger closing
if (‘closed‘ != this.readyState) {
// if we got data we‘re not polling
this.polling = false;
this.emit(‘pollComplete‘);
if (‘open‘ == this.readyState) {
this.poll();
} else {
debug(‘ignoring poll - transport state "%s"‘, this.readyState);
}
}
};
新的get请求已经在之前onData里面的poll()建立了。
如果有数据，立刻用send,以post请求的方式，将数据传给服务端。比如，聊天的文字。
post请求除了用来维持心跳，还负责将客户端的数据传给服务端，长连接的get请求已经单独发出了，不能用其传递数据了，就只有用post请求了。
然后是setPing()
Socket.prototype.setPing = function () {
var self = this;
clearTimeout(self.pingIntervalTimer);
self.pingIntervalTimer = setTimeout(function () {
debug(‘writing ping packet - expecting pong within %sms‘, self.pingTimeout);
self.ping();
self.onHeartbeat(self.pingTimeout);
}, self.pingInterval);
};
ping()用来向服务端发送心跳。
Socket.prototype.ping = function () {
this.sendPacket(‘ping‘);
};
至此，握手结束。
话说握手的时候，服务端会setPingTimeout();
Socket.prototype.setPingTimeout = function () {
var self = this;
clearTimeout(self.pingTimeoutTimer);
self.pingTimeoutTimer = setTimeout(function () {
self.onClose(‘ping timeout‘);
}, self.server.pingTimeout);
};
服务端会看在pingTimeout时间内，客户端有没有传送post请求，证明自己还在。
而客户端，在握手成功后，会setPing(),这个上面有。
然后等啊等，重要到pingInterval时间了，客户端发送post请求，this.sendPacket(‘ping‘);
另外，如果是客户端主动发送数据的话。
Socket.prototype.write =
Socket.prototype.send = function (msg, fn) {
this.sendPacket(‘message‘, msg, fn);
return this;
};
可以看到也是调用了sendPacket.
Socket.prototype.sendPacket = function (type, data, fn) {
if (‘closing‘ == this.readyState || ‘closed‘ == this.readyState) {
return;
}
var packet = { type: type, data: data };
this.emit(‘packetCreate‘, packet);
this.writeBuffer.push(packet);
this.callbackBuffer.push(fn);
this.flush();
};
Socket.prototype.flush = function () {
if (‘closed‘ != this.readyState && this.transport.writable &&
!this.upgrading && this.writeBuffer.length) {
debug(‘flushing %d packets in socket‘, this.writeBuffer.length);
this.transport.send(this.writeBuffer);
// keep track of current length of writeBuffer
// splice writeBuffer and callbackBuffer on `drain`
this.prevBufferLen = this.writeBuffer.length;
this.emit(‘flush‘);
}
};
然后flush()
Transport.prototype.send = function(packets){
if (‘open‘ == this.readyState) {
this.write(packets);
} else {
throw new Error(‘Transport not open‘);
}
};
Polling.prototype.write = function(packets){
var self = this;
this.writable = false;
var callbackfn = function() {
self.writable = true;
self.emit(‘drain‘);
};
var self = this;
parser.encodePayload(packets, this.supportsBinary, function(data) {
self.doWrite(data, callbackfn);
});
};
XHR.prototype.doWrite = function(data, fn){
var isBinary = typeof data !== ‘string‘ && data !== undefined;
var req = this.request({ method: ‘POST‘, data: data, isBinary: isBinary });
var self = this;
req.on(‘success‘, fn);
req.on(‘error‘, function(err){
self.onError(‘xhr post error‘, err);
});
this.sendXhr = req;
};
注意，这里request绑定了success事件，这个后面收到响应后会用到。
服务端收到ping后，结束长连接的get请求，并通过它发回pong响应。
xhr.onreadystatechange = function(){
if (4 != xhr.readyState) return;
if (200 == xhr.status || 1223 == xhr.status) {
self.onLoad();
} else {
// make sure the `error` event handler that‘s user-set
// does not throw in the same tick and gets caught here
setTimeout(function(){
self.onError(xhr.status);
}, 0);
}
};
Request.prototype.onLoad = function(){
var data;
try {
var contentType;
try {
contentType = this.xhr.getResponseHeader(‘Content-Type‘).split(‘;‘)[0];
} catch (e) {}
if (contentType === ‘application/octet-stream‘) {
data = this.xhr.response;
} else {
if (!this.supportsBinary) {
data = this.xhr.responseText;
} else {
data = ‘ok‘;
}
}
} catch (e) {
this.onError(e);
}
if (null != data) {
this.onData(data);
}
};
onLoad()取回发回的数据。
Request.prototype.onSuccess = function(){
this.emit(‘success‘);
this.cleanup();
};
Request.prototype.onData = function(data){
this.emit(‘data‘, data);
this.onSuccess();
};
注意，get请求上绑定data事件，用来接收数据；post请求上绑定success事件，用来确定接收服务端心跳成功。
对get请求，this.emit(‘data‘, data);这个在前面说收到握手响应的时候说过。只是最后解析出来的type是pong。
Socket.prototype.onPacket = function (packet) {
if (‘opening‘ == this.readyState || ‘open‘ == this.readyState) {
debug(‘socket receive: type "%s", data "%s"‘, packet.type, packet.data);
this.emit(‘packet‘, packet);
// Socket is live - any packet counts
this.emit(‘heartbeat‘);
switch (packet.type) {
case ‘open‘:
this.onHandshake(parsejson(packet.data));
break;
case ‘pong‘:
this.setPing();
break;
case ‘error‘:
var err = new Error(‘server error‘);
err.code = packet.data;
this.emit(‘error‘, err);
break;
case ‘message‘:
this.emit(‘data‘, packet.data);
this.emit(‘message‘, packet.data);
break;
}
} else {
debug(‘packet received with socket readyState "%s"‘, this.readyState);
}
};
然后setPing()设置发出post请求的定时器。
对post请求的响应。注意onSuccess（）里面this.emit(‘success‘);。这个在前面说发出post请求时，说到在request上绑定了success事件，这里就触发。回调函数是
var callbackfn = function() {
self.writable = true;
self.emit(‘drain‘);
};
transport
.on(‘drain‘, function(){
self.onDrain();
})
Socket.prototype.onDrain = function() {
...
this.writeBuffer.splice(0, this.prevBufferLen);
this.callbackBuffer.splice(0, this.prevBufferLen);
// setting prevBufferLen = 0 is very important
// for example, when upgrading, upgrade packet is sent over,
// and a nonzero prevBufferLen could cause problems on `drain`
this.prevBufferLen = 0;
if (this.writeBuffer.length == 0) {
this.emit(‘drain‘);
} else {
this.flush();
}
};
onDrain()里面会判断writeBuffer里有没有数据。道理和服务端onPollRequest()里面的this.emit("drain")一样，为了实时性。
最后说下，客户端新的get长连接请求是在什么时候发出的。
在解析get请求的响应时，self.onPacket()后并没有完，会调用poll()->doPoll().
Polling.prototype.onData = function(data){
var self = this;
debug(‘polling got data %s‘, data);
var callback = function(packet, index, total) {
// if its the first message we consider the transport open
if (‘opening‘ == self.readyState) {
self.onOpen();
}
// if its a close packet, we close the ongoing requests
if (‘close‘ == packet.type) {
self.onClose();
return false;
}
// otherwise bypass onData and handle the message
self.onPacket(packet);
};
// decode payload
parser.decodePayload(data, this.socket.binaryType, callback);
// if an event did not trigger closing
if (‘closed‘ != this.readyState) {
// if we got data we‘re not polling
this.polling = false;
this.emit(‘pollComplete‘);
if (‘open‘ == this.readyState) {
this.poll();
} else {
debug(‘ignoring poll - transport state "%s"‘, this.readyState);
}
}
};
至此，engine.io的客户端和服务端都简单的分析完了。
而里面的传输方式升级（polling->websocket）,两端的jsonp传输方式具体的执行，由于本屌时间精力有限，就没有做了。
如果前面的东西理解的话，这些分析其实一点都不难。
最后，可以看到socket.io 1.x在engine.io上加了不少东西，比如，broadcast,room,namespace等，看过这几篇文章后，相信这些加上去的东西也不难分析了。
时间： 2024-11-06 07:21:30