refactoring

redisson/src/test/java/org/redisson/SimpleDnsServer.java

@@ -9,15 +9,20 @@ import io.netty.handler.codec.dns.*;
 
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
+import java.util.concurrent.ThreadLocalRandom;
 
 public class SimpleDnsServer {
 
     private final EventLoopGroup group = new NioEventLoopGroup();
     private final Channel channel;
     private String ip = "127.0.0.1";
-    private final int port = 55;
+    private final int port;
 
     public SimpleDnsServer() throws InterruptedException {
+        this(ThreadLocalRandom.current().nextInt(50, 1000));
+    }
+
+    public SimpleDnsServer(int port) throws InterruptedException {
         Bootstrap bootstrap = new Bootstrap();
         bootstrap.group(group)
                 .channel(NioDatagramChannel.class)
@@ -30,6 +35,7 @@ public class SimpleDnsServer {
                     }
                 });
 
+        this.port = port;
         ChannelFuture future = bootstrap.bind(port).sync();
         channel = future.channel();
     }