net: Fix invalid write after end error

Don't error if not ended.

Fixes: #36029

lib/net.js

@@ -434,6 +434,10 @@ function afterShutdown() {
 // of the other side sending a FIN.  The standard 'write after end'
 // is overly vague, and makes it seem like the user's code is to blame.
 function writeAfterFIN(chunk, encoding, cb) {
+  if (!this.writabledEnded) {
+    return stream.Duplex.prototype.write.call(this, chunk, encoding, cb);
+  }
+
   if (typeof encoding === 'function') {
     cb = encoding;
     encoding = null;
@@ -947,7 +951,6 @@ Socket.prototype.connect = function(...args) {
   this._unrefTimer();
 
   this.connecting = true;
-  this.writable = true;
 
   if (pipe) {
     validateString(path, 'options.path');

test/parallel/test-net-writable.js

@@ -0,0 +1,16 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+
+const net = require('net');
+
+net.createServer(function(s) {
+  this.close();
+  s.end();
+}).listen(0, 'localhost', function() {
+  const socket = net.connect(this.address().port, 'localhost');
+  socket.on('end', common.mustCall(() => {
+    assert.strictEqual(socket.writable, true);
+    socket.write('hello world');
+  }));
+});

test/parallel/test-stream-transform-end.js

@@ -0,0 +1,20 @@
+'use strict';
+const common = require('../common');
+const { Readable, Transform } = require('stream');
+
+const src = new Readable({
+  read() {
+    this.push(Buffer.alloc(20000));
+  }
+});
+
+const dst = new Transform({
+  transform(chunk, output, fn) {
+    this.push(null);
+    fn();
+  }
+});
+
+src.pipe(dst);
+dst.resume();
+dst.once('end', common.mustCall());