判断Node.JS TCP Socket当前连接状态

Socket {
  connecting: false,
  _hadError: false,
  _handle:
   TCP {
     bytesRead: 0,
     _externalStream: {},
     fd: -1,
     reading: true,
     owner: [Circular],
     onread: [Function: onread],
     onconnection: null,
     writeQueueSize: 0 },
  _parent: null,
  _host: null,
  _readableState:
   ReadableState {
     objectMode: false,
     highWaterMark: 16384,
     buffer: BufferList { head: null, tail: null, length: 0 },
     length: 0,
     pipes: null,
     pipesCount: 0,
     flowing: true,
     ended: false,
     endEmitted: false,
     reading: false,
     sync: false,
     needReadable: true,
     emittedReadable: false,
     readableListening: false,
     resumeScheduled: false,
     defaultEncoding: 'utf8',
     ranOut: false,
     awaitDrain: 0,
     readingMore: false,
     decoder: null,
     encoding: null },
  readable: true,
  domain: null,
  _events:
   { end: [ [Object], [Function: onEnd] ],
     finish: [Function: onSocketFinish],
     _socketEnd: [Function: onSocketEnd],
     connect: [ [Function: onConnect] ],
     close: [Function: onClose],
     data: [Function: onData],
     drain: [Function: onDrain],
     error: [Function: onError],
     lookup: [Function: onLookup],
     timeout: [Function: onTimeout] },
  _eventsCount: 10,
  _maxListeners: undefined,
  _writableState:
   WritableState {
     objectMode: false,
     highWaterMark: 16384,
     needDrain: false,
     ending: false,
     ended: false,
     finished: false,
     decodeStrings: false,
     defaultEncoding: 'utf8',
     length: 0,
     writing: false,
     corked: 0,
     sync: true,
     bufferProcessing: false,
     onwrite: [Function],
     writecb: null,
     writelen: 0,
     bufferedRequest: null,
     lastBufferedRequest: null,
     pendingcb: 0,
     prefinished: true,
     errorEmitted: false,
     bufferedRequestCount: 0,
     corkedRequestsFree: CorkedRequest { next: null, entry: null, finish: [Function] } },
  writable: true,
  allowHalfOpen: false,
  destroyed: false,
  _bytesDispatched: 0,
  _sockname: null,
  _pendingData: null,
  _pendingEncoding: '',
  server: null,
  _server: null,
  read: [Function],
  _consuming: true,
  _idleNext: null,
  _idlePrev: null,
  _idleTimeout: -1,
  _peername: null }

Socket {
  connecting: false,
  _hadError: false,
  _handle: null,
  _parent: null,
  _host: null,
  _readableState: