Add receiver diagnostics and remote PicCap handover

tests/flatbuffer-proxy.py

@@ -0,0 +1,49 @@
+"""Test-only FlatBuffer TCP relay; accepts only the configured TV address."""
+import argparse
+import select
+import socket
+import socketserver
+
+parser = argparse.ArgumentParser()
+parser.add_argument('--bind', required=True)
+parser.add_argument('--port', type=int, default=19446)
+parser.add_argument('--upstream', required=True)
+parser.add_argument('--upstream-port', type=int, default=19400)
+args = parser.parse_args()
+
+
+class Relay(socketserver.BaseRequestHandler):
+    def handle(self):
+        if self.client_address[0] != args.upstream:
+            return
+        transferred = 0
+        try:
+            with socket.create_connection((args.upstream, args.upstream_port), timeout=3) as remote:
+                self.request.settimeout(3)
+                while True:
+                    readable, _, _ = select.select([self.request, remote], [], [], 3)
+                    if not readable:
+                        break
+                    for source in readable:
+                        data = source.recv(65536)
+                        if not data:
+                            return
+                        destination = remote if source is self.request else self.request
+                        destination.sendall(data)
+                        if source is self.request:
+                            if not transferred:
+                                print('PicCap FlatBuffer data received', flush=True)
+                            transferred += len(data)
+        except OSError:
+            pass
+        finally:
+            print(f'FlatBuffer connection closed: {transferred} bytes from TV', flush=True)
+
+
+class Server(socketserver.ThreadingTCPServer):
+    daemon_threads = True
+
+
+with Server((args.bind, args.port), Relay) as server:
+    print('FlatBuffer relay ready', flush=True)
+    server.serve_forever()