From 1e02fd7bc30fe2fe4834c5d9314c190061529d59 Mon Sep 17 00:00:00 2001
From: Jared Wiltshire <jazdw@users.noreply.github.com>
Date: Thu, 2 Nov 2023 12:49:10 -0600
Subject: [PATCH] Fail fast if transport is null, check for null on close

---
 .../serotonin/modbus4j/sero/messaging/MessageControl.java  | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/com/serotonin/modbus4j/sero/messaging/MessageControl.java b/src/com/serotonin/modbus4j/sero/messaging/MessageControl.java
index 4ec5d89..edaac11 100644
--- a/src/com/serotonin/modbus4j/sero/messaging/MessageControl.java
+++ b/src/com/serotonin/modbus4j/sero/messaging/MessageControl.java
@@ -52,6 +52,9 @@ public class MessageControl implements DataConsumer {
      */
     public void start(Transport transport, MessageParser messageParser, RequestHandler handler,
             WaitingRoomKeyFactory waitingRoomKeyFactory) throws IOException {
+        if (transport == null) {
+            throw new IllegalArgumentException("transport cannot be null");
+        }
         this.transport = transport;
         this.messageParser = messageParser;
         this.requestHandler = handler;
@@ -64,7 +67,9 @@ public void start(Transport transport, MessageParser messageParser, RequestHandl
      * <p>close.</p>
      */
     public void close() {
-        transport.removeConsumer();
+        if (transport != null) {
+            transport.removeConsumer();
+        }
     }
 
     /**