From 5d0e5cc1b17f25076e0af49b125c11c4e676aea8 Mon Sep 17 00:00:00 2001
From: Wayne Piekarski <wayne@tinmith.net>
Date: Wed, 14 Nov 2018 21:17:38 -0800
Subject: [PATCH] Implement the EXTPLANE-VERSION header to allow clients to
 know what features and bug fixes are available

---
 README.md                        |  9 +++++++--
 extplane-plugin/xplaneplugin.cpp |  5 ++++-
 extplane-server/tcpclient.cpp    |  4 +++-
 extplane-server/tcpserver.h      | 13 +++++++++++++
 4 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 4a7484a..595e969 100644
--- a/README.md
+++ b/README.md
@@ -182,7 +182,7 @@ scripts/cross-compile-win64-from-lin.sh for instructions.
 Launch X-Plane in console and observe the output. You should see something like:
 `ExtPlane-Plugin: Listening on port 51000`. All console output from Ext-Plane
 will start with `ExtPlane-Plugin`. Open another console and run `telnet localhost 51000`.
-Wait until you see line `EXTPLANE 1`. Then try typing the following commands:
+Wait until you see line `EXTPLANE 1` and `EXTPLANE-VERSION NNNNN`. Then try typing the following commands:
 
 ```
 sub sim/cockpit/electrical/night_vision_on
@@ -283,10 +283,15 @@ Supported settings are:
 
 ## Protocol Output ##
 
-* **EXTPLANE {version}**               Sent when connected. Version number is currently 1.
+* **EXTPLANE {protocol}**              Sent when connected. Protocol is currently 1.
+* **EXTPLANE-VERSION {version}**       Sent when connected. Feature version integer, which is incremented with each new bug fix or feature.
 * **u{type} {dataref} {value}**        Dataref has changed in value based on accuracy.
     * Types may be `i` (int), `f` (float), `d` (double), `ia` (int array), `fa` (float array), or `b` (data).
 
+The value for EXTPLANE-VERSION is defined in extplane-server/tcpserver.h. It is an integer and should be incremented
+each time new features are added or bugs are fixed. The client is then able to check if the version is new enough, and can
+warn the user if the plugin is out of date.
+
 ### Int/Float/Double Datarefs ###
 
 Example output:
diff --git a/extplane-plugin/xplaneplugin.cpp b/extplane-plugin/xplaneplugin.cpp
index c092734..92c30c6 100644
--- a/extplane-plugin/xplaneplugin.cpp
+++ b/extplane-plugin/xplaneplugin.cpp
@@ -44,7 +44,7 @@ int XPlanePlugin::pluginStart(char * outName, char * outSig, char *outDesc) {
     INFO << "Plugin started";
     strcpy(outName, "ExtPlane");
     strcpy(outSig, "org.vranki.extplaneplugin");
-    strcpy(outDesc, "Read and write X-Plane datarefs from external programs using TCP sockets.");
+    strcpy(outDesc, "Read and write X-Plane datarefs from external programs on TCP port " EXTPLANE_PORT_STR " with protocol " EXTPLANE_PROTOCOL_STR " version " EXTPLANE_VERSION_STR);
 
     // Init application and server
     app = new QCoreApplication(argc, &argv);
@@ -53,6 +53,9 @@ int XPlanePlugin::pluginStart(char * outName, char * outSig, char *outDesc) {
     server = new TcpServer(this, this);
     connect(server, SIGNAL(setFlightLoopInterval(float)), this, SLOT(setFlightLoopInterval(float)));
 
+    // Log that we have started
+    XPLMDebugString ("ExtPlane listening on TCP port " EXTPLANE_PORT_STR " with protocol " EXTPLANE_PROTOCOL_STR " version " EXTPLANE_VERSION_STR "\n");
+
     // Register the nav custom data accessors
     XPLMRegisterDataAccessor("extplane/navdata/5km",
                              xplmType_Data,                                 // The types we support
diff --git a/extplane-server/tcpclient.cpp b/extplane-server/tcpclient.cpp
index 3667c53..ca1d37b 100644
--- a/extplane-server/tcpclient.cpp
+++ b/extplane-server/tcpclient.cpp
@@ -1,4 +1,5 @@
 #include "tcpclient.h"
+#include "tcpserver.h"
 #include "datarefs/dataref.h"
 #include "datarefs/floatdataref.h"
 #include "datarefs/floatarraydataref.h"
@@ -23,7 +24,8 @@ TcpClient::TcpClient(QObject *parent,
 
     QByteArray block;
     QTextStream out(&block, QIODevice::WriteOnly);
-    out << "EXTPLANE 1\n";
+    out << "EXTPLANE " << EXTPLANE_PROTOCOL << "\n";
+    out << "EXTPLANE-VERSION " << EXTPLANE_VERSION << "\n";
     out.flush();
     _socket->write(block);
 }
diff --git a/extplane-server/tcpserver.h b/extplane-server/tcpserver.h
index bb83196..e461235 100644
--- a/extplane-server/tcpserver.h
+++ b/extplane-server/tcpserver.h
@@ -9,7 +9,20 @@
 /**
   * Creates the TCP socket and manages client connections
   */
+// TCP port used to listen for connections
 #define EXTPLANE_PORT 51000
+// Network protocol, currently always 1
+#define EXTPLANE_PROTOCOL 1
+// Feature revision, every time we add a new feature or bug fix, this should be incremented so that clients can know how old the plugin is
+#define EXTPLANE_VERSION 1000
+
+#define EXTPLANE_STRINGIFY(s) __EXTPLANE_STRINGIFY(s)
+#define __EXTPLANE_STRINGIFY(s) #s
+
+#define EXTPLANE_PORT_STR EXTPLANE_STRINGIFY(EXTPLANE_PORT)
+#define EXTPLANE_PROTOCOL_STR EXTPLANE_STRINGIFY(EXTPLANE_PROTOCOL)
+#define EXTPLANE_VERSION_STR EXTPLANE_STRINGIFY(EXTPLANE_VERSION)
+
 
 class TcpClient;
 class DataRefProvider;