[{"_1":2,"_3":-5,"_4":-5},"loaderData",{"_5":6,"_7":8},"actionData","errors","root",{"_11":-5,"_58":59,"_60":61,"_62":63},"routes/user.$name.collections",{"_9":10,"_11":12,"_13":14,"_15":16,"_17":18,"_19":16},"topics",[35],"user",{"_20":21,"_13":14,"_22":23,"_24":14,"_25":26,"_27":28,"_29":30,"_31":32,"_33":34},"loginname","oneWalker","page",1,"limit",20,"total","id","36278","avatar_url","https://avatars.githubusercontent.com/u/18098166?v=4","githubUsername","create_at","2019-03-17T15:20:55.658Z","score",185,"topic_count",6,"reply_count",31,"is_star",false,{"_20":36,"_37":38,"_39":40,"_41":42,"_43":44,"_45":46,"_47":48,"_49":34,"_31":50,"_51":52,"_25":53,"_54":55},"42025","author_id","35618","tab","share","content","```\r\ngithub:https://github.com/theanarkh/read-nodejs-code\r\n```\r\n下面是nodejs创建一个服务器的代码。接下来我们一起分析这个过程。\r\n```javascript\r\nvar http = require('http');\r\nhttp.createServer(function (request, response) {\r\n\tresponse.end('Hello World\\n');\r\n}).listen(9297);\r\n```\r\n首先我们去到lib/http.js模块看一下这个函数的代码。\r\n```javascript\r\nfunction createServer(requestListener) {\r\n return new Server(requestListener);\r\n}\r\n```\r\n只是对_http_server.js做了些封装。我们继续往下看。\r\n```javascript\r\nfunction Server(requestListener) {\r\n if (!(this instanceof Server)) return new Server(requestListener);\r\n net.Server.call(this, { allowHalfOpen: true });\r\n // 收到http请求时执行的回调\r\n if (requestListener) {\r\n this.on('request', requestListener);\r\n }\r\n\r\n this.httpAllowHalfOpen = false;\r\n // 建立tcp连接的回调\r\n this.on('connection', connectionListener);\r\n\r\n this.timeout = 2 * 60 * 1000;\r\n this.keepAliveTimeout = 5000;\r\n this._pendingResponseData = 0;\r\n this.maxHeadersCount = null;\r\n}\r\nutil.inherits(Server, net.Server);\r\n```\r\n发现_http_server.js也没有太多逻辑，继续看lib/net.js下的代码。\r\n```javascript\r\nfunction Server(options, connectionListener) {\r\n if (!(this instanceof Server))\r\n return new Server(options, connectionListener);\r\n\r\n EventEmitter.call(this);\r\n // connectionListener在http.js处理过了\r\n if (typeof options === 'function') {\r\n connectionListener = options;\r\n options = {};\r\n this.on('connection', connectionListener);\r\n } else if (options == null || typeof options === 'object') {\r\n options = options || {};\r\n\r\n if (typeof connectionListener === 'function') {\r\n this.on('connection', connectionListener);\r\n }\r\n } else {\r\n throw new errors.TypeError('ERR_INVALID_ARG_TYPE',\r\n 'options',\r\n 'Object',\r\n options);\r\n }\r\n\r\n this._connections = 0;\r\n ......\r\n this[async_id_symbol] = -1;\r\n this._handle = null;\r\n this._usingWorkers = false;\r\n this._workers = [];\r\n this._unref = false;\r\n\r\n this.allowHalfOpen = options.allowHalfOpen || false;\r\n this.pauseOnConnect = !!options.pauseOnConnect;\r\n}\r\n```\r\n至此http.createServer就执行结束了，我们发现这个过程还没有涉及到很多逻辑，并且还是停留到js层面。接下来我们继续分析listen函数的过程。该函数是net模块提供的。我们只看关键的代码。\r\n```c\r\nServer.prototype.listen = function(...args) {\r\n // 处理入参，根据文档我们知道listen可以接收好几个参数，我们这里是只传了端口号9297\r\n var normalized = normalizeArgs(args);\r\n // normalized = [{port: 9297}, null];\r\n var options = normalized[0];\r\n var cb = normalized[1];\r\n // 第一次listen的时候会创建，如果非空说明已经listen过\r\n if (this._handle) {\r\n throw new errors.Error('ERR_SERVER_ALREADY_LISTEN');\r\n }\r\n ......\r\n listenInCluster(this, null, options.port | 0, 4,\r\n backlog, undefined, options.exclusive);\r\n}\r\nfunction listenInCluster() {\r\n\t...\r\n\tserver._listen2(address, port, addressType, backlog, fd);\r\n}\r\n\r\n_listen2 = setupListenHandle = function() {\r\n\t......\r\n\tthis._handle = createServerHandle(...);\r\n\tthis._handle.listen(backlog || 511);\r\n}\r\nfunction createServerHandle() {\r\n\thandle = new TCP(TCPConstants.SERVER);\r\n\thandle.bind(address, port);\r\n}\r\n```\r\n到这我们终于看到了tcp连接的内容，每一个服务器新建一个handle并且保存他，该handle是一个TCP对象。然后执行bind和listen函数。接下来我们就看一下TCP类的代码。TCP是C++提供的类。对应的文件是tcp_wrap.cc。我们看看new TCP的时候发生了什么。\r\n```c\r\n\r\nvoid TCPWrap::New(const FunctionCallbackInfo& args) {\r\n // This constructor should not be exposed to public javascript.\r\n // Therefore we assert that we are not trying to call this as a\r\n // normal function.\r\n CHECK(args.IsConstructCall());\r\n CHECK(args[0]->IsInt32());\r\n Environment* env = Environment::GetCurrent(args);\r\n\r\n int type_value = args[0].As()->Value();\r\n TCPWrap::SocketType type = static_cast(type_value);\r\n\r\n ProviderType provider;\r\n switch (type) {\r\n case SOCKET:\r\n provider = PROVIDER_TCPWRAP;\r\n break;\r\n case SERVER:\r\n provider = PROVIDER_TCPSERVERWRAP;\r\n break;\r\n default:\r\n UNREACHABLE();\r\n }\r\n\r\n new TCPWrap(env, args.This(), provider);\r\n}\r\n\r\n\r\nTCPWrap::TCPWrap(Environment* env, Local