Add timeout_socket_server.py

This is a UNIX domain socket server that accepts connections and never
responds, so that we can test timeouts on the client side.

timeout_socket_server.py

@@ -0,0 +1,39 @@
+import socket
+import time
+import os
+
+server_address = './uds_socket'
+
+# Make sure the socket does not already exist
+try:
+    os.unlink(server_address)
+except OSError:
+    if os.path.exists(server_address):
+        raise
+
+sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+print('starting up on {}'.format(server_address))
+sock.bind(server_address)
+sock.listen(1)
+
+while True:
+    print('\nwaiting for a connection')
+
+    connection, client_address = sock.accept()
+    connection.settimeout(300)
+
+    try:
+        print('connected')
+        connect_time = time.time()
+        while True:
+            try:
+                data = connection.recv(640)
+                if not data:
+                    print('no data')
+                    break
+            except socket.timeout as exc:
+                elapsed_time = int(time.time() - connect_time)
+                print(f'timeout after {elapsed_time}s on recv')
+                break
+    finally:
+        connection.close()