net: rename internal functions for readability

* Rename listen to listenInCluster
* Rename _listen2 to _setupListenHandle
* Remove _listen since it's a one-liner only used in one place
* Correct comments in server.listen

PR-URL: https://github.com/nodejs/node/pull/11796
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/net.js

@@ -342,10 +342,11 @@ Socket.prototype.read = function(n) {
 };
 
 
+// FIXME(joyeecheung): this method is neither documented nor tested
 Socket.prototype.listen = function() {
   debug('socket.listen');
   this.on('connection', arguments[0]);
-  listen(this, null, null, null);
+  listenInCluster(this, null, null, null);
 };
 
 
@@ -1178,13 +1179,7 @@ util.inherits(Server, EventEmitter);
 
 function toNumber(x) { return (x = Number(x)) >= 0 ? x : false; }
 
-function _listen(handle, backlog) {
-  // Use a backlog of 512 entries. We pass 511 to the listen() call because
-  // the kernel does: backlogsize = roundup_pow_of_two(backlogsize + 1);
-  // which will thus give us a backlog of 512 entries.
-  return handle.listen(backlog || 511);
-}
-
+// Returns handle if it can be created, or error code if it can't
 function createServerHandle(address, port, addressType, fd) {
   var err = 0;
   // assign handle in listen, and clean up if bind or listen fails
@@ -1241,19 +1236,19 @@ function createServerHandle(address, port, addressType, fd) {
   return handle;
 }
 
-
-Server.prototype._listen2 = function(address, port, addressType, backlog, fd) {
-  debug('listen2', address, port, addressType, backlog, fd);
+function setupListenHandle(address, port, addressType, backlog, fd) {
+  debug('setupListenHandle', address, port, addressType, backlog, fd);
 
   // If there is not yet a handle, we need to create one and bind.
   // In the case of a server sent via IPC, we don't need to do this.
   if (this._handle) {
-    debug('_listen2: have a handle already');
+    debug('setupListenHandle: have a handle already');
   } else {
-    debug('_listen2: create a handle');
+    debug('setupListenHandle: create a handle');
 
     var rval = null;
 
+    // Try to bind to the unspecified IPv6 address, see if IPv6 is available
     if (!address && typeof fd !== 'number') {
       rval = createServerHandle('::', port, 6, fd);
 
@@ -1281,7 +1276,10 @@ Server.prototype._listen2 = function(address, port, addressType, backlog, fd) {
   this._handle.onconnection = onconnection;
   this._handle.owner = this;
 
-  var err = _listen(this._handle, backlog);
+  // Use a backlog of 512 entries. We pass 511 to the listen() call because
+  // the kernel does: backlogsize = roundup_pow_of_two(backlogsize + 1);
+  // which will thus give us a backlog of 512 entries.
+  var err = this._handle.listen(backlog || 511);
 
   if (err) {
     var ex = exceptionWithHostPort(err, 'listen', address, port);
@@ -1299,8 +1297,9 @@ Server.prototype._listen2 = function(address, port, addressType, backlog, fd) {
     this.unref();
 
   process.nextTick(emitListeningNT, this);
-};
+}
 
+Server.prototype._listen2 = setupListenHandle;  // legacy alias
 
 function emitErrorNT(self, err) {
   self.emit('error', err);
@@ -1314,25 +1313,32 @@ function emitListeningNT(self) {
 }
 
 
-function listen(self, address, port, addressType, backlog, fd, exclusive) {
+function listenInCluster(server, address, port, addressType,
+                         backlog, fd, exclusive) {
   exclusive = !!exclusive;
 
   if (!cluster) cluster = require('cluster');
 
   if (cluster.isMaster || exclusive) {
-    self._listen2(address, port, addressType, backlog, fd);
+    // Will create a new handle
+    // _listen2 sets up the listened handle, it is still named like this
+    // to avoid breaking code that wraps this method
+    server._listen2(address, port, addressType, backlog, fd);
     return;
   }
 
-  cluster._getServer(self, {
+  const serverQuery = {
     address: address,
     port: port,
     addressType: addressType,
     fd: fd,
     flags: 0
-  }, cb);
+  };
+
+  // Get the master's server handle, and listen on it
+  cluster._getServer(server, serverQuery, listenOnMasterHandle);
 
-  function cb(err, handle) {
+  function listenOnMasterHandle(err, handle) {
     // EADDRINUSE may not be reported until we call listen(). To complicate
     // matters, a failed bind() followed by listen() will implicitly bind to
     // a random port. Ergo, check that the socket is bound to the expected
@@ -1350,11 +1356,14 @@ function listen(self, address, port, addressType, backlog, fd, exclusive) {
 
     if (err) {
       var ex = exceptionWithHostPort(err, 'bind', address, port);
-      return self.emit('error', ex);
+      return server.emit('error', ex);
     }
 
-    self._handle = handle;
-    self._listen2(address, port, addressType, backlog, fd);
+    // Reuse master's server handle
+    server._handle = handle;
+    // _listen2 sets up the listened handle, it is still named like this
+    // to avoid breaking code that wraps this method
+    server._listen2(address, port, addressType, backlog, fd);
   }
 }
 
@@ -1381,12 +1390,12 @@ Server.prototype.listen = function() {
   // (handle[, backlog][, cb]) where handle is an object with a handle
   if (options instanceof TCP) {
     this._handle = options;
-    listen(this, null, -1, -1, backlogFromArgs);
+    listenInCluster(this, null, -1, -1, backlogFromArgs);
     return this;
   }
   // (handle[, backlog][, cb]) where handle is an object with a fd
   if (typeof options.fd === 'number' && options.fd >= 0) {
-    listen(this, null, null, null, backlogFromArgs, options.fd);
+    listenInCluster(this, null, null, null, backlogFromArgs, options.fd);
     return this;
   }
 
@@ -1411,8 +1420,9 @@ Server.prototype.listen = function() {
       lookupAndListen(this, options.port | 0, options.host, backlog,
                       options.exclusive);
     } else { // Undefined host, listens on unspecified address
-      listen(this, null, options.port | 0, 4, // addressType will be ignored
-             backlog, undefined, options.exclusive);
+      // Default addressType 4 will be used to search for master server
+      listenInCluster(this, null, options.port | 0, 4,
+                      backlog, undefined, options.exclusive);
     }
     return this;
   }
@@ -1422,7 +1432,8 @@ Server.prototype.listen = function() {
   if (options.path && isPipeName(options.path)) {
     const pipeName = this._pipeName = options.path;
     const backlog = options.backlog || backlogFromArgs;
-    listen(this, pipeName, -1, -1, backlog, undefined, options.exclusive);
+    listenInCluster(this, pipeName, -1, -1,
+                    backlog, undefined, options.exclusive);
     return this;
   }
 
@@ -1430,12 +1441,14 @@ Server.prototype.listen = function() {
 };
 
 function lookupAndListen(self, port, address, backlog, exclusive) {
-  require('dns').lookup(address, function doListening(err, ip, addressType) {
+  const dns = require('dns');
+  dns.lookup(address, function doListen(err, ip, addressType) {
     if (err) {
       self.emit('error', err);
     } else {
       addressType = ip ? addressType : 4;
-      listen(self, ip, port, addressType, backlog, undefined, exclusive);
+      listenInCluster(self, ip, port, addressType,
+                      backlog, undefined, exclusive);
     }
   });
 }