[hal] Add initial SystemServer support (#7463)

hal/src/main/native/systemcore/SystemServer.cpp

@@ -0,0 +1,35 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "SystemServer.h"
+
+#include "mrc/NtNetComm.h"
+
+namespace hal {
+
+static nt::NetworkTableInstance ServerInstance;
+
+void InitializeSystemServer() {
+  if (ServerInstance) {
+    return;
+  }
+  ServerInstance = nt::NetworkTableInstance::Create();
+  ServerInstance.SetServer("localhost", ROBOT_SYSTEM_SERVER_NT_PORT);
+  ServerInstance.StartClient4("RobotProgram");
+}
+
+void ShutdownSystemServer() {
+  if (!ServerInstance) {
+    return;
+  }
+
+  ServerInstance.StopClient();
+  nt::NetworkTableInstance::Destroy(ServerInstance);
+}
+
+nt::NetworkTableInstance GetSystemServer() {
+  return ServerInstance;
+}
+
+}  // namespace hal