Error: Call to a member function send() on null in

'''Error: Call to a member function send() on null in /home/vw/src/gjsj/web-msg-sender/vendor/workerman/phpsocket.io/src/Engine/Transports/WebSocket.php:39'''
'''Stack trace:'''
'''#0 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/phpsocket.io/src/Engine/Socket.php(318): PHPSocketIO\Engine\Transports\WebSocket->send(Array)'''
'''#1 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/phpsocket.io/src/Engine/Socket.php(79): PHPSocketIO\Engine\Socket->flush()'''
'''#2 [internal function]: PHPSocketIO\Engine\Socket->onUpgradePacket(Array)'''
'''#3 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/phpsocket.io/src/Event/Emitter.php(93): call_user_func_array(Array, Array)'''
'''#4 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/phpsocket.io/src/Engine/Transport.php(56): PHPSocketIO\Event\Emitter->emit('packet', Array)'''
'''#5 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/phpsocket.io/src/Engine/Transport.php(61): PHPSocketIO\Engine\Transport->onPacket(Array)'''
'''#6 [internal function]: PHPSocketIO\Engine\Transport->onData('5')'''
'''#7 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/phpsocket.io/src/Engine/Transports/WebSocket.php(26): call_user_func(Array, '5')'''
'''#8 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/workerman/Connection/TcpConnection.php(656): PHPSocketIO\Engine\Transports\WebSocket->onData2(Object(Workerman\Connection\TcpConnection), '5')'''
'''#9 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/workerman/Events/Select.php(292): Workerman\Connection\TcpConnection->baseRead(Resource id #7185)'''
'''#10 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/workerman/Worker.php(2399): Workerman\Events\Select->loop()'''
'''#11 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/workerman/Worker.php(1534): Workerman\Worker->run()'''
'''#12 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/workerman/Worker.php(1364): Workerman\Worker::forkOneWorkerForLinux(Object(Workerman\Worker))'''
'''#13 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/workerman/Worker.php(1338): Workerman\Worker::forkWorkersForLinux()'''
'''#14 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/workerman/Worker.php(1668): Workerman\Worker::forkWorkers()'''
'''#15 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/workerman/Worker.php(1617): Workerman\Worker::monitorWorkersForLinux()'''
'''#16 /home/vw/src/gjsj/web-msg-sender/vendor/workerman/workerman/Worker.php(541): Workerman\Worker::monitorWorkers()'''
'''#17 /home/vw/src/gjsj/web-msg-sender/start.php(27): Workerman\Worker::runAll()'''
'''#18 {main}'''
Worker[27827] process terminated
worker[PHPSocketIO:27827] exit with status 64000

'''