PVA: Add sequence to 'echo'

core/pva/src/main/java/org/epics/pva/client/ClientTCPHandler.java

@@ -98,7 +98,8 @@ class ClientTCPHandler extends TCPHandler
     /** Time [ms] when this client sent last message to server */
     private volatile long last_message_sent;
 
-    private static final RequestEncoder echo_request = new EchoRequest();
+    /** Creates echo requests, tracks the counter for this TCP connection */
+    private final EchoRequest echo_request = new EchoRequest();
 
     /** Indicates completion of the connection validation:
      *  Server sent connection validation request,
@@ -112,7 +113,7 @@ class ClientTCPHandler extends TCPHandler
     public ClientTCPHandler(final PVAClient client, final InetSocketAddress address, final Guid guid, final boolean tls) throws Exception
     {
         super(createSocket(address, tls), true);
-        logger.log(Level.FINE, () -> "TCPHandler " + guid + " for " + address + " created ============================");
+        logger.log(Level.FINE, () -> "TCPHandler " + (tls ? "(TLS) " : "") + guid + " for " + address + " created ============================");
         this.client = client;
         this.guid = guid;
 
@@ -248,7 +249,7 @@ private void checkResponsiveness()
         if (idle > PVASettings.EPICS_PVA_CONN_TMO * 1000)
         {
             // If silent for full EPICS_CA_CONN_TMO, disconnect and start over
-            logger.log(Level.FINE, () -> this + " silent for " + idle + "ms, closing");
+            logger.log(Level.FINE, () -> this + " idle for " + idle + "ms, closing");
             client.shutdownConnection(this);
             return;
         }
@@ -268,13 +269,13 @@ private void checkResponsiveness()
             request_echo = true;
         }
 
-        // How long have we been silent, which could case the server to close connection?
+        // How long have we been silent, which could cause the server to close connection?
         final long silent = now - last_message_sent;
         if (! request_echo  &&  silent >= PVASettings.EPICS_PVA_CONN_TMO * 1000 / 2)
         {
             // With default EPICS_CA_CONN_TMO of 30 seconds,
-            // Echo requested every 15 seconds.
-            logger.log(Level.FINE, () -> "Client to " + this + " silent for " + silent + "ms, requesting echo");
+            // Echo sent every 15 seconds to inform server that this client is still alive.
+            logger.log(Level.FINE, () -> "Client to " + this + " silent for " + silent + "ms, sending echo");
             request_echo = true;
         }
 
@@ -289,6 +290,12 @@ private void checkResponsiveness()
         }
     }
 
+    /** @return Most recently sent echo request */
+    String getActiveEchoRequest()
+    {
+        return echo_request.getActiveRequest();
+    }
+
     /** Called whenever e.g. value is received and server is thus alive */
     void markAlive()
     {

core/pva/src/main/java/org/epics/pva/client/ClientUDPHandler.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2019-2023 Oak Ridge National Laboratory.
+ * Copyright (c) 2019-2025 Oak Ridge National Laboratory.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -16,6 +16,7 @@
 import java.net.StandardSocketOptions;
 import java.nio.ByteBuffer;
 import java.nio.channels.DatagramChannel;
+import java.util.Arrays;
 import java.util.logging.Level;
 
 import org.epics.pva.PVASettings;
@@ -337,7 +338,15 @@ private boolean handleSearchReply(final InetSocketAddress from, final byte versi
 
             // Server may reply with list of PVs that it does _not_ have...
             if (! response.found)
-                search_response.handleSearchResponse(-1, server, version, response.guid, response.tls);
+            {
+                // Did server provide list of channels that it _doesn't_ know?!
+                if (response.cid.length > 0)
+                    logger.log(Level.FINE,
+                               "Server " + from + " sent search reply for not-found channels " +
+                               Arrays.toString(response.cid));
+                else // Server simply indicates its presence, no channel detail
+                    search_response.handleSearchResponse(-1, server, version, response.guid, response.tls);
+            }
             else
                 for (int cid : response.cid)
                     search_response.handleSearchResponse(cid, server, version, response.guid, response.tls);

core/pva/src/main/java/org/epics/pva/client/EchoHandler.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2019 Oak Ridge National Laboratory.
+ * Copyright (c) 2019-2025 Oak Ridge National Laboratory.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -37,11 +37,12 @@ public void handleCommand(final ClientTCPHandler tcp, final ByteBuffer buffer) t
         {
             final byte[] payload = new byte[payload_size];
             buffer.get(payload);
-            if (Arrays.equals(payload, EchoRequest.CHECK))
+            final String expected = tcp.getActiveEchoRequest();
+            if (Arrays.equals(payload, expected.getBytes()))
                 logger.log(Level.FINE, () -> "Received ECHO:\n" + Hexdump.toHexdump(payload));
             else
             {
-                logger.log(Level.WARNING, this + " received invalid echo reply:\n" +
+                logger.log(Level.WARNING, this + " received invalid echo reply, expected " + expected + ":\n" +
                                           Hexdump.toHexdump(payload));
                 return;
             }

core/pva/src/main/java/org/epics/pva/client/EchoRequest.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2019 Oak Ridge National Laboratory.
+ * Copyright (c) 2019-2025 Oak Ridge National Laboratory.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -10,6 +10,7 @@
 import static org.epics.pva.PVASettings.logger;
 
 import java.nio.ByteBuffer;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.logging.Level;
 
 import org.epics.pva.common.PVAHeader;
@@ -21,7 +22,9 @@
 @SuppressWarnings("nls")
 class EchoRequest implements RequestEncoder
 {
-    static final byte[] CHECK = new byte[] { 'e', 'c', 'h', 'o' };
+    // Random number so replies don't all start with 'echo00'
+    private final AtomicInteger counter = new AtomicInteger((int)(Math.random() * 100));
+    private volatile String active_check = "";
 
     @Override
     public void encodeRequest(final byte version, final ByteBuffer buffer) throws Exception
@@ -33,10 +36,19 @@ public void encodeRequest(final byte version, final ByteBuffer buffer) throws Ex
             PVAHeader.encodeMessageHeader(buffer, PVAHeader.FLAG_NONE, PVAHeader.CMD_ECHO, 0);
         }
         else
-        {
+        {   // Issue next 'echo12'
+            final int count = counter.incrementAndGet();
+            active_check = String.format("echo%02d",  count % 100);
+            final byte[] check = active_check.getBytes();
             logger.log(Level.FINE, () -> "Sending ECHO request (Version " + version + ")");
-            PVAHeader.encodeMessageHeader(buffer, PVAHeader.FLAG_NONE, PVAHeader.CMD_ECHO, CHECK.length);
-            buffer.put(CHECK);
+            PVAHeader.encodeMessageHeader(buffer, PVAHeader.FLAG_NONE, PVAHeader.CMD_ECHO, check.length);
+            buffer.put(check);
         }
     }
+
+    /** @return Most recently sent echo request */
+    public String getActiveRequest()
+    {
+        return active_check;
+    }
 }

core/pva/src/main/java/org/epics/pva/client/PVAClient.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2019-2023 Oak Ridge National Laboratory.
+ * Copyright (c) 2019-2025 Oak Ridge National Laboratory.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -124,9 +124,9 @@ public Collection<ServerInfo> list(final TimeUnit unit, final long duration) thr
         return list_replies.values();
     }
 
-    private void handleListResponse(final InetSocketAddress server, final int version, final Guid guid)
+    private void handleListResponse(final InetSocketAddress server, final int version, final Guid guid, final boolean tls)
     {
-        logger.log(Level.FINE, () -> guid + " version " + version + ": tcp@" + server);
+        logger.log(Level.FINE, () -> "Server list response: " + guid + " version " + version + ", tcp@" + server + (tls ? " (TLS)" : ""));
         final ServerInfo info = list_replies.computeIfAbsent(guid, g -> new ServerInfo(g));
         info.version = version;
         info.addresses.add(server);
@@ -221,7 +221,7 @@ void handleSearchResponse(final int channel_id, final InetSocketAddress server,
         // Generic server 'list' response?
         if (channel_id < 0)
         {
-            handleListResponse(server, version, guid);
+            handleListResponse(server, version, guid, tls);
             return;
         }