Add configurable hostname lookup

Signed-off-by: James Tomson <[email protected]>

org.eclipse.paho.client.mqttv3/src/main/java/org/eclipse/paho/client/mqttv3/IMqttDns.java

@@ -0,0 +1,8 @@
+package org.eclipse.paho.client.mqttv3;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+public interface IMqttDns {
+    InetAddress lookup(String host) throws UnknownHostException;
+}

org.eclipse.paho.client.mqttv3/src/main/java/org/eclipse/paho/client/mqttv3/MqttConnectOptions.java

@@ -74,6 +74,7 @@ public class MqttConnectOptions {
 	private boolean automaticReconnect = false;
 	private int maxReconnectDelay = 128000;
 	private Properties customWebSocketHeaders = null;
+	private IMqttDns dns = null;
 
 	// Client Operation Parameters
 	private int executorServiceTimeout = 1; // How long to wait in seconds when terminating the executor service.
@@ -646,6 +647,14 @@ public int getExecutorServiceTimeout() {
 		return executorServiceTimeout;
 	}
 
+	public IMqttDns getDns() {
+		return dns;
+	}
+
+	public void setDns(IMqttDns dns) {
+		this.dns = dns;
+	}
+
 	/**
 	 * Set the time in seconds that the executor service should wait when
 	 * terminating before forcefully terminating. It is not recommended to change
@@ -679,6 +688,11 @@ public Properties getDebug() {
 		} else {
 			p.put("SSLProperties", getSSLProperties());
 		}
+		if (getDns() == null) {
+			p.put("Dns", strNull);
+		} else {
+			p.put("Dns", getDns());
+		}
 		return p;
 	}
 

org.eclipse.paho.client.mqttv3/src/main/java/org/eclipse/paho/client/mqttv3/internal/TCPNetworkModule.java

@@ -22,9 +22,11 @@
 import java.net.InetSocketAddress;
 import java.net.Socket;
 import java.net.SocketAddress;
+import java.net.InetAddress;
 
 import javax.net.SocketFactory;
 
+import org.eclipse.paho.client.mqttv3.IMqttDns;
 import org.eclipse.paho.client.mqttv3.MqttException;
 import org.eclipse.paho.client.mqttv3.logging.Logger;
 import org.eclipse.paho.client.mqttv3.logging.LoggerFactory;
@@ -41,6 +43,7 @@ public class TCPNetworkModule implements NetworkModule {
 	private String host;
 	private int port;
 	private int conTimeout;
+	private IMqttDns dns;
 
 	/**
 	 * Constructs a new TCPNetworkModule using the specified host and
@@ -59,6 +62,14 @@ public TCPNetworkModule(SocketFactory factory, String host, int port, String res
 
 	}
 
+	public TCPNetworkModule(SocketFactory factory, String host, int port, String resourceContext, IMqttDns dns) {
+		log.setResourceName(resourceContext);
+		this.factory = factory;
+		this.host = host;
+		this.port = port;
+		this.dns = dns;
+	}
+
 	/**
 	 * Starts the module, by creating a TCP socket to the server.
 	 * @throws IOException if there is an error creating the socket
@@ -69,7 +80,13 @@ public void start() throws IOException, MqttException {
 		try {
 			// @TRACE 252=connect to host {0} port {1} timeout {2}
 			log.fine(CLASS_NAME,methodName, "252", new Object[] {host, Integer.valueOf(port), Long.valueOf(conTimeout*1000)});
-			SocketAddress sockaddr = new InetSocketAddress(host, port);
+			final SocketAddress sockaddr;
+			if (dns != null) {
+				InetAddress inetAddr = dns.lookup(host);
+				sockaddr = new InetSocketAddress(inetAddr, port);
+			} else {
+				sockaddr = new InetSocketAddress(host, port); // default system resolver
+			}
 			socket = factory.createSocket();
 			socket.connect(sockaddr, conTimeout*1000);
 			socket.setSoTimeout(1000);

org.eclipse.paho.client.mqttv3/src/main/java/org/eclipse/paho/client/mqttv3/internal/TCPNetworkModuleFactory.java

@@ -56,7 +56,7 @@ public NetworkModule createNetworkModule(URI brokerUri, MqttConnectOptions optio
 		} else if (factory instanceof SSLSocketFactory) {
 			throw ExceptionHelper.createMqttException(MqttException.REASON_CODE_SOCKET_FACTORY_MISMATCH);
 		}
-		TCPNetworkModule networkModule = new TCPNetworkModule(factory, host, port, clientId);
+		TCPNetworkModule networkModule = new TCPNetworkModule(factory, host, port, clientId, options.getDns());
 		networkModule.setConnectTimeout(options.getConnectionTimeout());
 		return networkModule;
 	}