Potential fix for an issue where the telnet client was reconnecting right at the same time we try to shut down spothole, causing the stop() method to close one telnet object but then a new one is created and read from anyway.

providers/spot/dxcluster.py

@@ -1,7 +1,7 @@
 import logging
 import re
 from datetime import datetime
-from threading import Event, Thread
+from threading import Event, Lock, Thread
 
 import pytz
 import telnetlib3
@@ -40,6 +40,7 @@ class DXCluster(SpotProvider):
             self._LINE_PATTERN_ALLOW_RBN if self._allow_rbn_spots else self._LINE_PATTERN_EXCLUDE_RBN
         )
         self._telnet = None
+        self._telnet_lock = Lock()
         self._thread = None
         self._stop_event = Event()
 
@@ -49,8 +50,9 @@ class DXCluster(SpotProvider):
 
     def stop(self):
         self._stop_event.set()
-        if self._telnet:
-            self._telnet.close()
+        with self._telnet_lock:
+            if self._telnet:
+                self._telnet.close()
         if self._thread:
             self._thread.join(timeout=15)
             if self._thread.is_alive():
@@ -63,7 +65,14 @@ class DXCluster(SpotProvider):
                 try:
                     self.status = "Connecting"
                     logger.info(f"DX Cluster {self._hostname} connecting...")
-                    self._telnet = telnetlib3.Telnet(self._hostname, self._port)
+                    new_telnet = telnetlib3.Telnet(self._hostname, self._port)
+                    with self._telnet_lock:
+                        self._telnet = new_telnet
+                        if self._stop_event.is_set():
+                            # stop() was called while we were connecting, close the connection rather than trying to
+                            # read when we know it won't work
+                            new_telnet.close()
+                            break
                     self._telnet.read_until(self._login_prompt.encode("latin-1"))
                     self._telnet.write(f"{self._login_callsign}\n".encode("latin-1"))
                     connected = True