Add reverse connect command line support to ConsoleReferenceServer (#3376)

* Add reverse connect command line parameter to ConsoleReferenceServer

Co-authored-by: romanett <[email protected]>

* Add reverse connect documentation for console server and client

Co-authored-by: romanett <[email protected]>

* Add error handling for invalid reverse connect URL

Co-authored-by: romanett <[email protected]>

* Resolve merge conflicts with master branch

Co-authored-by: marcschier <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: romanett <[email protected]>
Co-authored-by: marcschier <[email protected]>
Co-authored-by: Marc Schier <[email protected]>

Author: 3 people

Applications/ConsoleReferenceClient/README.md

@@ -7,6 +7,34 @@ Some of these parameters are explained in more detail below.
 
 To see all available parameters call console reference client with the parameter `-h`.
 
+## Reverse Connect
+
+The OPC UA reverse connect feature allows an OPC UA server to initiate the connection to a client, rather than the traditional model where clients connect to servers. This is particularly useful in scenarios where the server is behind a firewall or NAT, making it difficult for clients to directly connect to it.
+
+### How to use Reverse Connect
+
+To enable reverse connect mode, specify the client endpoint URL using the `--rc` or `--reverseconnect` parameter:
+
+```bash
+dotnet ConsoleReferenceClient.dll --rc=opc.tcp://localhost:65300 opc.tcp://localhost:62541/Quickstarts/ReferenceServer
+```
+
+The client will start a reverse connect listener on the specified endpoint (e.g., `opc.tcp://localhost:65300`) and wait for the server to connect to it.
+
+### Example: Client and Server with Reverse Connect
+
+1. Start the client with reverse connect listener on port 65300:
+   ```bash
+   dotnet ConsoleReferenceClient.dll --rc=opc.tcp://localhost:65300 opc.tcp://localhost:62541/Quickstarts/ReferenceServer
+   ```
+
+2. In a separate terminal, start the server with reverse connect to the client:
+   ```bash
+   dotnet ConsoleReferenceServer.dll --rc=opc.tcp://localhost:65300 -a
+   ```
+
+The server will establish a reverse connection to the client endpoint, and the client will use this connection to communicate with the server.
+
 ### How to specify User Identity
 #### Username & Password
 Specify as console parameters:
@@ -18,3 +46,4 @@ Place your user certificate in the TrustedUserCertificatesStore (the path can be
 Specify console parameters:
     `-uc Thumbprint` (of the user certificate to select)
     `-ucp Password` (of the user certificates private key (optional))
+

Applications/ConsoleReferenceServer/Program.cs

@@ -72,6 +72,7 @@ public static async Task<int> Main(string[] args)
             bool provisioningMode = false;
             char[] password = null;
             int timeout = -1;
+            string reverseConnectUrlString = null;
 
             string usage = Utils.IsRunningOnMono()
                 ? $"Usage: mono {applicationName}.exe [OPTIONS]"
@@ -98,6 +99,11 @@ public static async Task<int> Main(string[] args)
                     "provision",
                     "start server in provisioning mode with limited namespace for certificate provisioning",
                     p => provisioningMode = p != null
+                },
+                {
+                    "rc|reverseconnect=",
+                    "Connect to the specified client endpoint for reverse connect. (e.g. rc=opc.tcp://localhost:65300)",
+                    url => reverseConnectUrlString = url
                 }
             };
 
@@ -185,6 +191,24 @@ await server
                 logger.LogInformation("Start the server.");
                 await server.StartAsync().ConfigureAwait(false);
 
+                // setup reverse connect if specified
+                if (!string.IsNullOrEmpty(reverseConnectUrlString))
+                {
+                    try
+                    {
+                        logger.LogInformation("Adding reverse connection to {Url}.", reverseConnectUrlString);
+                        var reverseConnectUrl = new Uri(reverseConnectUrlString);
+                        server.Server.AddReverseConnection(reverseConnectUrl);
+                    }
+                    catch (UriFormatException ex)
+                    {
+                        logger.LogError(ex, "Invalid reverse connect URL: {Url}", reverseConnectUrlString);
+                        throw new ErrorExitException(
+                            $"Invalid reverse connect URL: {reverseConnectUrlString}",
+                            ExitCode.ErrorInvalidCommandLine);
+                    }
+                }
+
                 // Apply custom settings for CTT testing
                 if (cttMode)
                 {

Applications/ConsoleReferenceServer/README.md

@@ -0,0 +1,49 @@
+# OPC Foundation UA .NET Standard Reference Server
+
+## Introduction
+
+The console reference server can be configured using several console parameters.
+Some of these parameters are explained in more detail below.
+
+To see all available parameters call console reference server with the parameter `-h`.
+
+## Reverse Connect
+
+The OPC UA reverse connect feature allows an OPC UA server to initiate the connection to a client, rather than the traditional model where clients connect to servers. This is particularly useful in scenarios where the server is behind a firewall or NAT, making it difficult for clients to directly connect to it.
+
+### How to use Reverse Connect
+
+To enable reverse connect mode, specify the client endpoint URL using the `--rc` or `--reverseconnect` parameter:
+
+```bash
+dotnet ConsoleReferenceServer.dll --rc=opc.tcp://localhost:65300
+```
+
+or
+
+```bash
+dotnet ConsoleReferenceServer.dll --reverseconnect=opc.tcp://localhost:65300
+```
+
+### Example: Server and Client with Reverse Connect
+
+1. Start the client with reverse connect listener on port 65300:
+   ```bash
+   dotnet ConsoleReferenceClient.dll --rc=opc.tcp://localhost:65300 opc.tcp://localhost:62541/Quickstarts/ReferenceServer
+   ```
+
+2. In a separate terminal, start the server with reverse connect to the client:
+   ```bash
+   dotnet ConsoleReferenceServer.dll --rc=opc.tcp://localhost:65300 -a
+   ```
+
+The server will establish a reverse connection to the client endpoint, and the client will use this connection to communicate with the server.
+
+### Additional Options
+
+- `-a` or `--autoaccept`: Auto accept untrusted certificates (for testing only)
+- `-c` or `--console`: Log to console
+- `-l` or `--log`: Log app output
+- `-t` or `--timeout`: Timeout in seconds to exit application
+
+For the complete list of options, use `--help`.