[ntcore] Add ability to announce mDNS for server

glass/src/libnt/native/cpp/NetworkTablesSettings.cpp

@@ -80,7 +80,7 @@ void NetworkTablesSettings::Thread::Main() {
       }
     } else if (m_mode == 3) {
       wpi::nt::StartServer(m_inst, m_iniName.c_str(), m_listenAddress.c_str(),
-                           m_port);
+                           "", m_port);
     }
   }
 }

ntcore/src/dev/native/cpp/main.cpp

@@ -87,7 +87,7 @@ void bench() {
   auto server = wpi::nt::CreateInstance();
 
   // connect client and server
-  wpi::nt::StartServer(server, "bench.json", "127.0.0.1", 10000);
+  wpi::nt::StartServer(server, "bench.json", "127.0.0.1", "", 10000);
   wpi::nt::StartClient(client, "client");
   wpi::nt::SetServer(client, "127.0.0.1", 10000);
 
@@ -150,7 +150,7 @@ void bench2() {
   auto server = wpi::nt::CreateInstance();
 
   // connect client and server
-  wpi::nt::StartServer(server, "bench2.json", "127.0.0.1", 10000);
+  wpi::nt::StartServer(server, "bench2.json", "127.0.0.1", "", 10000);
   wpi::nt::StartClient(client1, "client1");
   wpi::nt::StartClient(client2, "client2");
   wpi::nt::SetServer(client1, "127.0.0.1", 10000);
@@ -223,7 +223,7 @@ static std::uniform_real_distribution<double> dist;
 
 void stress() {
   auto server = wpi::nt::CreateInstance();
-  wpi::nt::StartServer(server, "stress.json", "127.0.0.1", 10000);
+  wpi::nt::StartServer(server, "stress.json", "127.0.0.1", "", 10000);
   wpi::nt::SubscribeMultiple(server, {{std::string_view{}}});
 
   using namespace std::chrono_literals;
@@ -344,7 +344,7 @@ void latency() {
   auto server = wpi::nt::CreateInstance();
 
   // connect client and server
-  wpi::nt::StartServer(server, "latency.json", "127.0.0.1", 10000);
+  wpi::nt::StartServer(server, "latency.json", "127.0.0.1", "", 10000);
   wpi::nt::StartClient(client1, "client1");
   wpi::nt::SetServer(client1, "127.0.0.1", 10000);
   wpi::nt::StartClient(client2, "client2");

ntcore/src/generate/main/java/NetworkTableInstance.java.jinja

@@ -891,7 +891,7 @@ public final class NetworkTableInstance implements AutoCloseable {
    * @param persistFilename the name of the persist file to use
    */
   public void startServer(String persistFilename) {
-    startServer(persistFilename, "");
+    startServer(persistFilename, "", "");
   }
 
   /**
@@ -901,18 +901,32 @@ public final class NetworkTableInstance implements AutoCloseable {
    * @param listenAddress the address to listen on, or empty to listen on any address
    */
   public void startServer(String persistFilename, String listenAddress) {
-    startServer(persistFilename, listenAddress, kDefaultPort);
+    startServer(persistFilename, listenAddress, "");
   }
 
   /**
-   * Starts a server using the specified filename, listening address, and port.
+   * Starts a server using the specified filename, listening address, and mdns service,
+   * using the default port.
    *
    * @param persistFilename the name of the persist file to use
    * @param listenAddress the address to listen on, or empty to listen on any address
+   * @param mdnsService the mDNS service name to advertise, or empty to not advertise
+   */
+  public void startServer(String persistFilename, String listenAddress, String mdnsService) {
+    startServer(persistFilename, listenAddress, mdnsService, kDefaultPort);
+  }
+
+  /**
+   * Starts a server using the specified filename, listening address, mdns service and port.
+   *
+   * @param persistFilename the name of the persist file to use
+   * @param listenAddress the address to listen on, or empty to listen on any address
+   * @param mdnsService the mDNS service name to advertise, or empty to not advertise
    * @param port port to communicate over
    */
-  public void startServer(String persistFilename, String listenAddress, int port) {
-    NetworkTablesJNI.startServer(m_handle, persistFilename, listenAddress, port);
+  public void startServer(String persistFilename, String listenAddress, String mdnsService,
+      int port) {
+    NetworkTablesJNI.startServer(m_handle, persistFilename, listenAddress, mdnsService, port);
   }
 
   /** Stops the server if it is running. */

ntcore/src/generate/main/java/NetworkTablesJNI.java.jinja

@@ -864,10 +864,11 @@ public final class NetworkTablesJNI {
    * @param inst NT instance handle.
    * @param persistFilename the name of the persist file to use
    * @param listenAddress the address to listen on, or empty to listen on any address
+   * @param mdnsService the mDNS service name to advertise, or empty to not advertise
    * @param port port to communicate over
    */
   public static native void startServer(
-      int inst, String persistFilename, String listenAddress, int port);
+      int inst, String persistFilename, String listenAddress, String mdnsService, int port);
 
   /**
    * Stops the server if it is running.

ntcore/src/main/native/cpp/InstanceImpl.cpp

@@ -103,16 +103,20 @@ void InstanceImpl::StopLocal() {
 
 void InstanceImpl::StartServer(std::string_view persistFilename,
                                std::string_view listenAddress,
+                               std::string_view mdnsService,
                                unsigned int port) {
   std::scoped_lock lock{m_mutex};
   if (networkMode != NT_NET_MODE_NONE) {
     return;
   }
   m_networkServer = std::make_shared<NetworkServer>(
-      persistFilename, listenAddress, port, localStorage, connectionList,
-      logger, [this] {
+      persistFilename, listenAddress, mdnsService, port, localStorage,
+      connectionList, logger, [this](bool announcingmDNS) {
         std::scoped_lock lock{m_mutex};
         networkMode &= ~NT_NET_MODE_STARTING;
+        if (announcingmDNS) {
+          networkMode |= NT_NET_MODE_MDNS_ANNOUNCING;
+        }
       });
   networkMode = NT_NET_MODE_SERVER | NT_NET_MODE_STARTING;
   listenerStorage.NotifyTimeSync({}, NT_EVENT_TIMESYNC, 0, 0, true);

ntcore/src/main/native/cpp/InstanceImpl.hpp

@@ -44,7 +44,8 @@ class InstanceImpl {
   void StartLocal();
   void StopLocal();
   void StartServer(std::string_view persistFilename,
-                   std::string_view listenAddress, unsigned int port);
+                   std::string_view listenAddress, std::string_view mdnsService,
+                   unsigned int port);
   void StopServer();
   void StartClient(std::string_view identity);
   void StopClient();

ntcore/src/main/native/cpp/NetworkServer.cpp

@@ -253,17 +253,19 @@ void NetworkServer::ServerConnection4::ProcessWsUpgrade() {
 }
 
 NetworkServer::NetworkServer(std::string_view persistentFilename,
-                             std::string_view listenAddress, unsigned int port,
+                             std::string_view listenAddress,
+                             std::string_view mdnsService, unsigned int port,
                              net::ILocalStorage& localStorage,
                              IConnectionList& connList,
                              wpi::util::Logger& logger,
-                             std::function<void()> initDone)
+                             std::function<void(bool)> initDone)
     : m_localStorage{localStorage},
       m_connList{connList},
       m_logger{logger},
       m_initDone{std::move(initDone)},
       m_persistentFilename{persistentFilename},
       m_listenAddress{wpi::util::trim(listenAddress)},
+      m_mdnsService{wpi::util::trim(mdnsService)},
       m_port{port},
       m_serverImpl{logger},
       m_localQueue{logger},
@@ -462,9 +464,23 @@ void NetworkServer::Init() {
     tcp4->Listen();
   }
 
+  bool announcingmDNS = false;
+  if (!m_mdnsService.empty()) {
+    m_mdnsAnnouncer.emplace(m_mdnsService, "_networktables._tcp", m_port);
+    if (!m_mdnsAnnouncer->HasImplementation()) {
+      WARN("mDNS service announcer not available; cannot announce '{}'",
+           m_mdnsService);
+      m_mdnsAnnouncer.reset();
+    } else {
+      m_mdnsAnnouncer->Start();
+      announcingmDNS = true;
+      INFO("mDNS announcing as service '{}' on port {}", m_mdnsService, m_port);
+    }
+  }
+
   if (m_initDone) {
     DEBUG4("NetworkServer initDone()");
-    m_initDone();
+    m_initDone(announcingmDNS);
     m_initDone = nullptr;
   }
 }

ntcore/src/main/native/cpp/NetworkServer.hpp

@@ -7,6 +7,7 @@
 #include <atomic>
 #include <functional>
 #include <memory>
+#include <optional>
 #include <string>
 #include <string_view>
 #include <vector>
@@ -15,6 +16,7 @@
 #include "net/Message.hpp"
 #include "server/ServerImpl.hpp"
 #include "wpi/net/EventLoopRunner.hpp"
+#include "wpi/net/MulticastServiceAnnouncer.h"
 #include "wpi/net/uv/Async.hpp"
 #include "wpi/net/uv/Idle.hpp"
 #include "wpi/net/uv/Timer.hpp"
@@ -35,9 +37,10 @@ class IConnectionList;
 class NetworkServer {
  public:
   NetworkServer(std::string_view persistentFilename,
-                std::string_view listenAddress, unsigned int port,
-                net::ILocalStorage& localStorage, IConnectionList& connList,
-                wpi::util::Logger& logger, std::function<void()> initDone);
+                std::string_view listenAddress, std::string_view mdnsService,
+                unsigned int port, net::ILocalStorage& localStorage,
+                IConnectionList& connList, wpi::util::Logger& logger,
+                std::function<void(bool)> initDone);
   ~NetworkServer();
 
   void FlushLocal();
@@ -57,13 +60,15 @@ class NetworkServer {
   net::ILocalStorage& m_localStorage;
   IConnectionList& m_connList;
   wpi::util::Logger& m_logger;
-  std::function<void()> m_initDone;
+  std::function<void(bool)> m_initDone;
   std::string m_persistentData;
   std::string m_persistentFilename;
   std::string m_listenAddress;
+  std::string m_mdnsService;
   unsigned int m_port;
 
   // used only from loop
+  std::optional<wpi::net::MulticastServiceAnnouncer> m_mdnsAnnouncer;
   std::shared_ptr<wpi::net::uv::Timer> m_readLocalTimer;
   std::shared_ptr<wpi::net::uv::Timer> m_savePersistentTimer;
   std::shared_ptr<wpi::net::uv::Async<>> m_flushLocal;

ntcore/src/main/native/cpp/jni/NetworkTablesJNI.cpp

@@ -1178,12 +1178,12 @@ Java_org_wpilib_networktables_NetworkTablesJNI_stopLocal
 /*
  * Class:     org_wpilib_networktables_NetworkTablesJNI
  * Method:    startServer
- * Signature: (ILjava/lang/String;Ljava/lang/String;I)V
+ * Signature: (ILjava/lang/String;Ljava/lang/String;Ljava/lang/String;I)V
  */
 JNIEXPORT void JNICALL
 Java_org_wpilib_networktables_NetworkTablesJNI_startServer
   (JNIEnv* env, jclass, jint inst, jstring persistFilename,
-   jstring listenAddress, jint port)
+   jstring listenAddress, jstring mdnsService, jint port)
 {
   if (!persistFilename) {
     nullPointerEx.Throw(env, "persistFilename cannot be null");
@@ -1193,8 +1193,13 @@ Java_org_wpilib_networktables_NetworkTablesJNI_startServer
     nullPointerEx.Throw(env, "listenAddress cannot be null");
     return;
   }
+  if (!mdnsService) {
+    nullPointerEx.Throw(env, "mdnsService cannot be null");
+    return;
+  }
   wpi::nt::StartServer(inst, JStringRef{env, persistFilename}.str(),
-                       JStringRef{env, listenAddress}.c_str(), port);
+                       JStringRef{env, listenAddress}.c_str(),
+                       JStringRef{env, mdnsService}.c_str(), port);
 }
 
 /*

ntcore/src/main/native/cpp/ntcore_c.cpp

@@ -532,9 +532,10 @@ void NT_StopLocal(NT_Inst inst) {
 
 void NT_StartServer(NT_Inst inst, const struct WPI_String* persist_filename,
                     const struct WPI_String* listen_address,
-                    unsigned int port) {
+                    const struct WPI_String* mdns_service, unsigned int port) {
   wpi::nt::StartServer(inst, wpi::util::to_string_view(persist_filename),
-                       wpi::util::to_string_view(listen_address), port);
+                       wpi::util::to_string_view(listen_address),
+                       wpi::util::to_string_view(mdns_service), port);
 }
 
 void NT_StopServer(NT_Inst inst) {

ntcore/src/main/native/cpp/ntcore_cpp.cpp

@@ -633,9 +633,10 @@ void StopLocal(NT_Inst inst) {
 }
 
 void StartServer(NT_Inst inst, std::string_view persist_filename,
-                 std::string_view listen_address, unsigned int port) {
+                 std::string_view listen_address, std::string_view mdns_service,
+                 unsigned int port) {
   if (auto ii = InstanceImpl::GetTyped(inst, Handle::kInstance)) {
-    ii->StartServer(persist_filename, listen_address, port);
+    ii->StartServer(persist_filename, listen_address, mdns_service, port);
   }
 }
 

ntcore/src/main/native/include/wpi/nt/NetworkTableInstance.hpp

@@ -607,12 +607,17 @@ class NetworkTableInstance final {
    * @param listen_address    the address to listen on, or an empty string to
    *                          listen on any address. (UTF-8 string, null
    *                          terminated)
+   * @param mdns_service      the mDNS service name to announce, or an empty
+   *                          string to not announce via mDNS (UTF-8 string,
+   *                          null terminated)
    * @param port              port to communicate over
    */
   void StartServer(std::string_view persist_filename = "networktables.json",
                    const char* listen_address = "",
+                   const char* mdns_service = "",
                    unsigned int port = kDefaultPort) {
-    ::wpi::nt::StartServer(m_handle, persist_filename, listen_address, port);
+    ::wpi::nt::StartServer(m_handle, persist_filename, listen_address,
+                           mdns_service, port);
   }
 
   /**

ntcore/src/main/native/include/wpi/nt/ntcore_c.h

@@ -90,6 +90,7 @@ enum NT_NetworkMode {
   NT_NET_MODE_CLIENT = 0x04,   /* running in client mode */
   NT_NET_MODE_STARTING = 0x08, /* flag for starting (either client or server) */
   NT_NET_MODE_LOCAL = 0x10,    /* running in local-only mode */
+  NT_NET_MODE_MDNS_ANNOUNCING = 0x20 /* mDNS is enabled and announcing */
 };
 
 /** Event notification flags. */
@@ -1116,10 +1117,14 @@ void NT_StopLocal(NT_Inst inst);
  * @param listen_address    the address to listen on, or an empty string to
  *                          listen on any address. (UTF-8 string, null
  *                          terminated)
+ * @param mdns_service      the mDNS service name to advertise, or an empty
+ *                          string to not advertise via mDNS. (UTF-8 string,
+ *                          null terminated)
  * @param port              port to communicate over
  */
 void NT_StartServer(NT_Inst inst, const struct WPI_String* persist_filename,
-                    const struct WPI_String* listen_address, unsigned int port);
+                    const struct WPI_String* listen_address,
+                    const struct WPI_String* mdns_service, unsigned int port);
 
 /**
  * Stops the server if it is running.