[hal] Add initial SystemServer support (#7463)

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

@@ -27,11 +27,11 @@
 
 #include "HALInitializer.h"
 #include "HALInternal.h"
+#include "SystemServer.h"
 #include "hal/DriverStation.h"
 #include "hal/Errors.h"
 #include "hal/Notifier.h"
 #include "hal/handles/HandlesInternal.h"
-#include "hal/roborio/HMB.h"
 
 using namespace hal;
 
@@ -337,6 +337,8 @@ HAL_Bool HAL_Initialize(int32_t timeout, int32_t mode) {
 
   prctl(PR_SET_PDEATHSIG, SIGTERM);
 
+  hal::InitializeSystemServer();
+
   // // Return false if program failed to kill an existing program
   // if (!killExistingProgram(timeout, mode)) {
   //   return false;

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

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

@@ -0,0 +1,13 @@
+// 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.
+
+#pragma once
+
+#include <networktables/NetworkTableInstance.h>
+
+namespace hal {
+void InitializeSystemServer();
+void ShutdownSystemServer();
+nt::NetworkTableInstance GetSystemServer();
+}  // namespace hal