diff --git a/logisim/logisim-debugger/src/main/java/org/cdm/logisim/debugger/server/Server.java b/logisim/logisim-debugger/src/main/java/org/cdm/logisim/debugger/server/Server.java
index 65f1b3f..d8097fc 100644
--- a/logisim/logisim-debugger/src/main/java/org/cdm/logisim/debugger/server/Server.java
+++ b/logisim/logisim-debugger/src/main/java/org/cdm/logisim/debugger/server/Server.java
@@ -84,7 +84,7 @@ public void onStart() {
     }
 
     public void sendMessage(String message) {
-        if (currentConnection != null) {
+        if (currentConnection != null && currentConnection.isOpen()) {
             currentConnection.send(message);
         }
     }