Major plugin refactor and cleanup.

Switched to POCO library for unified platform/library interface.
Deprecated the external module API. It was creating more problems than solving.
Removed most built-in libraries in favor of system libraries for easier maintenance.
Cleaned and secured code with help from static analyzers.

vendor/POCO/Net/testsuite/src/UDPEchoServer.cpp

@@ -0,0 +1,83 @@
+//
+// UDPEchoServer.cpp
+//
+// Copyright (c) 2005-2006, Applied Informatics Software Engineering GmbH.
+// and Contributors.
+//
+// SPDX-License-Identifier:	BSL-1.0
+//
+
+
+#include "UDPEchoServer.h"
+#include "Poco/Net/SocketAddress.h"
+#include "Poco/Timespan.h"
+#include <iostream>
+
+
+using Poco::Net::Socket;
+using Poco::Net::DatagramSocket;
+using Poco::Net::SocketAddress;
+using Poco::Net::IPAddress;
+
+
+UDPEchoServer::UDPEchoServer():
+	_thread("UDPEchoServer"),
+	_stop(false)
+{
+	_socket.bind(SocketAddress(), true);
+	_thread.start(*this);
+	_ready.wait();
+}
+
+
+UDPEchoServer::UDPEchoServer(const SocketAddress& sa):
+	_thread("UDPEchoServer"),
+	_stop(false)
+{
+	_socket.bind(sa, true);
+	_thread.start(*this);
+	_ready.wait();
+}
+
+
+UDPEchoServer::~UDPEchoServer()
+{
+	_stop = true;
+	_thread.join();
+}
+
+
+Poco::UInt16 UDPEchoServer::port() const
+{
+	return _socket.address().port();
+}
+
+
+void UDPEchoServer::run()
+{
+	Poco::Timespan span(250000);
+	while (!_stop)
+	{
+		_ready.set();
+		if (_socket.poll(span, Socket::SELECT_READ))
+		{
+			try
+			{
+				char buffer[256];
+				SocketAddress sender;
+				int n = _socket.receiveFrom(buffer, sizeof(buffer), sender);
+				n = _socket.sendTo(buffer, n, sender);
+			}
+			catch (Poco::Exception& exc)
+			{
+				std::cerr << "UDPEchoServer: " << exc.displayText() << std::endl;
+			}
+		}
+	}
+}
+
+
+SocketAddress UDPEchoServer::address() const
+{
+	return _socket.address();
+}