net: improve socket.write() error message

lib/net.js

@@ -619,8 +619,10 @@ Socket.prototype.__defineGetter__('localPort', function() {
 
 
 Socket.prototype.write = function(chunk, encoding, cb) {
-  if (typeof chunk !== 'string' && !(chunk instanceof Buffer))
-    throw new TypeError('Invalid data');
+  if (typeof chunk !== 'string' && !(chunk instanceof Buffer)) {
+    throw new TypeError(
+      'Invalid data, chunk must be a string or buffer, not ' + typeof chunk);
+  }
   return stream.Duplex.prototype.write.apply(this, arguments);
 };
 

test/parallel/test-net-socket-write-error.js

@@ -0,0 +1,18 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const net = require('net');
+
+const server = net.createServer().listen(common.PORT, connectToServer);
+
+function connectToServer() {
+  const client = net.createConnection(common.PORT, () => {
+    assert.throws(() => {
+      client.write(1337);
+    }, /Invalid data, chunk must be a string or buffer, not number/);
+
+    client.end();
+  })
+  .on('end', () => server.close());
+}