From 03bd5e604846944cc4cccb6a5dc143410e41a3f9 Mon Sep 17 00:00:00 2001
From: Mitch Gaffigan <mitch.gaffigan@comcast.net>
Date: Sat, 17 Oct 2026 15:54:48 -0500
Subject: [PATCH] Configure idle keepalive timers to traverse nat

Signed-off-by: Mitch Gaffigan <mitch.gaffigan@comcast.net>
---
 .../connect/connectors/tcp/SocketUtil.java    | 21 +++++++++++++++++++
 .../connect/connectors/tcp/TcpDispatcher.java |  6 ++++--
 .../connect/connectors/tcp/TcpReceiver.java   |  4 +++-
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/server/src/main/java/com/mirth/connect/connectors/tcp/SocketUtil.java b/server/src/main/java/com/mirth/connect/connectors/tcp/SocketUtil.java
index a9830e4d7f..ae5f6301a2 100644
--- a/server/src/main/java/com/mirth/connect/connectors/tcp/SocketUtil.java
+++ b/server/src/main/java/com/mirth/connect/connectors/tcp/SocketUtil.java
@@ -13,14 +13,21 @@
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.Socket;
+import java.net.SocketException;
 import java.net.UnknownHostException;
 
 import org.apache.commons.lang3.StringUtils;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 
 import com.mirth.connect.util.TcpUtil;
 
+import jdk.net.ExtendedSocketOptions;
+
 public class SocketUtil {
 
+    private static final Logger logger = LogManager.getLogger(SocketUtil.class);
+
     public static Socket createSocket(TcpConfiguration configuration) throws UnknownHostException, IOException {
         return createSocket(configuration, null);
     }
@@ -67,6 +74,20 @@ public static void connectSocket(Socket socket, String host, int port, int timeo
         socket.connect(new InetSocketAddress(InetAddress.getByName(TcpUtil.getFixedHost(host)), port), timeout);
     }
 
+    /** Set TCP keepalive options on a socket */
+    public static void setKeepAlive(Socket socket) throws SocketException {
+        socket.setKeepAlive(true);
+
+        try {
+            int keepAliveIdle = Integer.parseInt(System.getProperty("mirth.tcp.keepalive.idle", "120").trim());
+            if (keepAliveIdle > 0) {
+                socket.setOption(ExtendedSocketOptions.TCP_KEEPIDLE, keepAliveIdle);
+            }
+        } catch (Exception e) {
+            logger.warn("Failed to set TCP keepalive options on socket.", e);
+        }
+    }
+
     public static void closeSocket(Socket socket) throws IOException {
         if (socket != null) {
             /*
diff --git a/server/src/main/java/com/mirth/connect/connectors/tcp/TcpDispatcher.java b/server/src/main/java/com/mirth/connect/connectors/tcp/TcpDispatcher.java
index 16dd25a411..067b0aca7e 100644
--- a/server/src/main/java/com/mirth/connect/connectors/tcp/TcpDispatcher.java
+++ b/server/src/main/java/com/mirth/connect/connectors/tcp/TcpDispatcher.java
@@ -376,7 +376,9 @@ public Response send(ConnectorProperties connectorProperties, ConnectorMessage m
                     socket.setReceiveBufferSize(bufferSize);
                     socket.setSendBufferSize(bufferSize);
                     socket.setSoTimeout(responseTimeout);
-                    socket.setKeepAlive(tcpDispatcherProperties.isKeepConnectionOpen());
+                    if (tcpDispatcherProperties.isKeepConnectionOpen()) {
+                        SocketUtil.setKeepAlive(socket);
+                    }
 
                     eventController.dispatchEvent(new ConnectorCountEvent(getChannelId(), getMetaDataId(), getDestinationName(), ConnectionStatusEventType.CONNECTED, SocketUtil.getLocalAddress(socket) + " -> " + SocketUtil.getInetAddress(socket), true));
                 }
@@ -810,7 +812,7 @@ private void initSocket(Socket socket) throws SocketException {
         socket.setReceiveBufferSize(bufferSize);
         socket.setSendBufferSize(bufferSize);
         socket.setSoTimeout(responseTimeout);
-        socket.setKeepAlive(true);
+        SocketUtil.setKeepAlive(socket);
         socket.setReuseAddress(true);
         socket.setTcpNoDelay(true);
     }
diff --git a/server/src/main/java/com/mirth/connect/connectors/tcp/TcpReceiver.java b/server/src/main/java/com/mirth/connect/connectors/tcp/TcpReceiver.java
index 66f48433db..57a46c5222 100644
--- a/server/src/main/java/com/mirth/connect/connectors/tcp/TcpReceiver.java
+++ b/server/src/main/java/com/mirth/connect/connectors/tcp/TcpReceiver.java
@@ -1067,7 +1067,9 @@ private void initSocket(Socket socket) throws SocketException {
         socket.setReceiveBufferSize(bufferSize);
         socket.setSendBufferSize(bufferSize);
         socket.setSoTimeout(timeout);
-        socket.setKeepAlive(connectorProperties.isKeepConnectionOpen());
+        if (connectorProperties.isKeepConnectionOpen()) {
+            SocketUtil.setKeepAlive(socket);
+        }
         socket.setReuseAddress(true);
         socket.setTcpNoDelay(true);
     }