diff --git a/core/src/main/java/org/bitcoinj/testing/TestWithPeerGroup.java b/core/src/main/java/org/bitcoinj/testing/TestWithPeerGroup.java
index acbc8451..0d7b5691 100644
--- a/core/src/main/java/org/bitcoinj/testing/TestWithPeerGroup.java
+++ b/core/src/main/java/org/bitcoinj/testing/TestWithPeerGroup.java
@@ -80,6 +80,7 @@ protected void initPeerGroup() {
             peerGroup = new PeerGroup(unitTestParams, blockChain, new BlockingClientManager());
         peerGroup.setPingIntervalMsec(0);  // Disable the pings as they just get in the way of most tests.
         peerGroup.addWallet(wallet);
+        peerGroup.setUseLocalhostPeerWhenPossible(false); // Prevents from connecting to bitcoin nodes on localhost.
     }
 
     protected InboundMessageQueuer connectPeerWithoutVersionExchange(int id) throws Exception {
diff --git a/core/src/test/java/org/bitcoinj/core/FilteredBlockAndPartialMerkleTreeTests.java b/core/src/test/java/org/bitcoinj/core/FilteredBlockAndPartialMerkleTreeTests.java
index c62c16e4..f994d8e9 100644
--- a/core/src/test/java/org/bitcoinj/core/FilteredBlockAndPartialMerkleTreeTests.java
+++ b/core/src/test/java/org/bitcoinj/core/FilteredBlockAndPartialMerkleTreeTests.java
@@ -141,6 +141,8 @@ public void serializeDownloadBlockWithWallet() throws Exception {
         super.setUp(blockStore);
         
         peerGroup.addWallet(wallet);
+        peerGroup.setUseLocalhostPeerWhenPossible(false); // Prevents from connecting to bitcoin nodes on localhost.
+
         blockChain.addWallet(wallet);
 
         peerGroup.startAsync();
diff --git a/core/src/test/java/org/bitcoinj/core/PeerGroupTest.java b/core/src/test/java/org/bitcoinj/core/PeerGroupTest.java
index 562d60d2..58f2595f 100644
--- a/core/src/test/java/org/bitcoinj/core/PeerGroupTest.java
+++ b/core/src/test/java/org/bitcoinj/core/PeerGroupTest.java
@@ -36,6 +36,7 @@
 import org.junit.runners.Parameterized;
 
 import java.io.IOException;
+import java.net.BindException;
 import java.net.InetSocketAddress;
 import java.net.ServerSocket;
 import java.util.*;
@@ -686,9 +687,24 @@ public void waitForPeersOfVersion() throws Exception {
 
     @Test
     public void preferLocalPeer() throws IOException {
-        // Check that if we have a localhost port 8333 then it's used instead of the p2p network.
-        ServerSocket local = new ServerSocket(params.getPort(), 100, InetAddresses.forString("127.0.0.1"));
+        // Because we are using the same port (8333 or 18333) that is used by Satoshi client
+        // We have to consider 2 cases:
+        // 1. Test are executed on the same machine that is running full node / Satoshi client
+        // 2. Test are executed without any full node running locally
+        // We have to avoid to connecting to real and external services in unit tests
+        // So we skip this test in case we have already something running on port params.getPort()
+
+        // Check that if we have a localhost port 8333 or 18333 then it's used instead of the p2p network.
+        ServerSocket local = null;
         try {
+            local = new ServerSocket(params.getPort(), 100, InetAddresses.forString("127.0.0.1"));
+        }
+        catch(BindException e) { // Port already in use, skipping this test.
+            return;
+        }
+
+        try {
+            peerGroup.setUseLocalhostPeerWhenPossible(true);
             peerGroup.startAsync();
             peerGroup.awaitRunning();
             local.accept().close();   // Probe connect