Document net.Socket() constructor

doc/api/net.markdown

@@ -163,6 +163,21 @@ and passed to the user through the `'connection'` event of a server.
 
 `net.Socket` instances are EventEmitters with the following events:
 
+#### new net.Socket([options])
+
+Construct a new socket object.
+
+`options` is an object with the following defaults:
+
+    { fd: null
+      type: null
+      allowHalfOpen: false
+    }
+
+`fd` allows you to specify the existing file descriptor of socket. `type`
+specified underlying protocol. It can be `'tcp4'`, `'tcp6'`, or `'unix'`.
+About `allowHalfOpen`, refer to `createServer()` and `'end'` event.
+
 #### socket.connect(port, [host], [callback])
 #### socket.connect(path, [callback])