[wpiutil] Add mDNS resolver and announcer (#3733)

wpiutil/src/main/java/edu/wpi/first/util/MulticastServiceResolver.java

@@ -0,0 +1,44 @@
+// 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.
+
+package edu.wpi.first.util;
+
+/** Class to resolve a service over mDNS. */
+public class MulticastServiceResolver implements AutoCloseable {
+  private final int m_handle;
+
+  /**
+   * Creates a MulticastServiceResolver.
+   *
+   * @param serviceType service type to look for
+   */
+  public MulticastServiceResolver(String serviceType) {
+    m_handle = WPIUtilJNI.createMulticastServiceResolver(serviceType);
+  }
+
+  @Override
+  public void close() {
+    WPIUtilJNI.freeMulticastServiceResolver(m_handle);
+  }
+
+  public void start() {
+    WPIUtilJNI.startMulticastServiceResolver(m_handle);
+  }
+
+  public void stop() {
+    WPIUtilJNI.stopMulticastServiceResolver(m_handle);
+  }
+
+  public boolean hasImplementation() {
+    return WPIUtilJNI.getMulticastServiceResolverHasImplementation(m_handle);
+  }
+
+  public int getEventHandle() {
+    return WPIUtilJNI.getMulticastServiceResolverEventHandle(m_handle);
+  }
+
+  public ServiceData getData() {
+    return WPIUtilJNI.getMulticastServiceResolverData(m_handle);
+  }
+}