Implementing reverse tunnel to the remote host

scripts/mcp-http-howto.md

@@ -151,6 +151,7 @@ If you want MCP to be strictly read-only, consider removing or guarding those `m
 ## Troubleshooting
 - If a dialog field isn’t found, check the exact label in `/mcp/dialog` output.
 - If the server doesn’t respond, verify the plugin is running and the port is open.
+- MCP startup log line `MCP: local-only (no reverse SSH tunnel detected; see mcp-remote-ssh-tunnel.md)` indicates a reverse tunnel is not running.
 
 ## Forward plan (single host → multi-host)
 - **Single host first**: keep MCP local and use it to supervise runs and inspect outputs.

src/main/java/com/elphel/imagej/mcp/McpServer.java

@@ -33,10 +33,50 @@ public class McpServer {
         McpFsAccess.ensureConfigured();
         McpServer instance = new McpServer(owner, port);
         instance.start();
+        if (hasReverseSshTunnel(port)) {
+            System.out.println("MCP: reverse SSH tunnel detected for port " + port);
+        } else {
+            System.out.println("MCP: local-only (no reverse SSH tunnel detected; see mcp-remote-ssh-tunnel.md)");
+        }
         INSTANCE = instance;
         return instance;
     }
 
+    private static boolean hasReverseSshTunnel(int port) {
+        String needle = "127.0.0.1:" + port + ":127.0.0.1:" + port;
+        final boolean[] found = new boolean[] { false };
+        java.lang.ProcessHandle.allProcesses().forEach(handle -> {
+            if (found[0]) {
+                return;
+            }
+            java.lang.ProcessHandle.Info info = handle.info();
+            if (!info.command().isPresent()) {
+                return;
+            }
+            String cmd = info.command().orElse("");
+            if (!cmd.endsWith("ssh")) {
+                return;
+            }
+            String[] args = info.arguments().orElse(new String[0]);
+            if (args.length == 0) {
+                return;
+            }
+            boolean hasR = false;
+            boolean hasMatch = false;
+            for (String arg : args) {
+                if ("-R".equals(arg)) {
+                    hasR = true;
+                } else if (arg.contains(needle)) {
+                    hasMatch = true;
+                }
+            }
+            if (hasR && hasMatch) {
+                found[0] = true;
+            }
+        });
+        return found[0];
+    }
+
     private McpServer(Eyesis_Correction owner, int port) {
         this.owner = owner;
         this.port = port;