net: add local family

doc/api/net.md

@@ -294,6 +294,7 @@ TCP server, the argument is as follows, otherwise the argument is `undefined`.
 * `data` {Object} The argument passed to event listener.
  * `localAddress` {string} Local address.
  * `localPort` {number} Local port.
+ * `localFamily` {string} Local family.
  * `remoteAddress` {string} Remote address.
  * `remotePort` {number} Remote port.
  * `remoteFamily` {string} Remote IP family. `'IPv4'` or `'IPv6'`.
@@ -1047,6 +1048,16 @@ added: v0.9.6
 
 The numeric representation of the local port. For example, `80` or `21`.
 
+### `socket.localFamily`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* {string}
+
+The string representation of the local IP family. `'IPv4'` or `'IPv6'`.
+
 ### `socket.pause()`
 
 * Returns: {net.Socket} The socket itself.

lib/net.js

@@ -834,6 +834,9 @@ protoGetter('localPort', function localPort() {
  return this._getsockname().port;
 });
 
+protoGetter('localFamily', function localFamily() {
+ return this._getsockname().family;
+});
 
 Socket.prototype[kAfterAsyncWrite] = function() {
  this[kLastWriteQueueSize] = 0;
@@ -1668,6 +1671,7 @@ function onconnection(err, clientHandle) {
  clientHandle.getsockname(localInfo);
  data.localAddress = localInfo.address;
  data.localPort = localInfo.port;
+ data.localFamily = localInfo.family;
  }
  if (clientHandle.getpeername) {
  const remoteInfo = ObjectCreate(null);

test/parallel/test-net-local-address-port.js

@@ -27,6 +27,7 @@ const net = require('net');
 const server = net.createServer(common.mustCall(function(socket) {
  assert.strictEqual(socket.localAddress, common.localhostIPv4);
  assert.strictEqual(socket.localPort, this.address().port);
+ assert.strictEqual(socket.localFamily, this.address().family);
  socket.on('end', function() {
  server.close();
  });