diff --git a/libethereum/Client.cpp b/libethereum/Client.cpp
index 187f3dfad..b4c06279b 100644
--- a/libethereum/Client.cpp
+++ b/libethereum/Client.cpp
@@ -99,7 +99,8 @@ void Client::startNetwork(unsigned short _listenPort, std::string const& _seedHo
 	catch (std::exception const&)
 	{
 		// Probably already have the port open.
-		m_net.reset(new PeerServer(m_clientVersion, m_bc, 0, _mode));
+		cwarn << "Could not initialize with specified/default port. Trying system-assigned port";
+		m_net.reset(new PeerServer(m_clientVersion, m_bc, 0, _mode, _publicIP, _upnp));
 	}
 
 	m_net->setIdealPeerCount(_peers);
diff --git a/libethereum/PeerServer.cpp b/libethereum/PeerServer.cpp
index b27a93e28..be8e4a96f 100644
--- a/libethereum/PeerServer.cpp
+++ b/libethereum/PeerServer.cpp
@@ -71,6 +71,25 @@ PeerServer::PeerServer(std::string const& _clientVersion, BlockChain const& _ch,
 	clog(NetNote) << "Id:" << toHex(m_key.address().ref().cropped(0, 4)) << "Mode: " << (_m == NodeMode::PeerServer ? "PeerServer" : "Full");
 }
 
+PeerServer::PeerServer(std::string const& _clientVersion, BlockChain const& _ch, unsigned int _networkId, NodeMode _m, string const& _publicAddress, bool _upnp):
+	m_clientVersion(_clientVersion),
+	m_mode(_m),
+	m_listenPort(0),
+	m_chain(&_ch),
+	m_acceptor(m_ioService, bi::tcp::endpoint(bi::tcp::v4(), 0)),
+	m_socket(m_ioService),
+	m_key(KeyPair::create()),
+	m_networkId(_networkId)
+{
+	m_listenPort = m_acceptor.local_endpoint().port();
+
+	// populate addresses.
+	populateAddresses();
+	determinePublic(_publicAddress, _upnp);
+	ensureAccepting();
+	clog(NetNote) << "Id:" << toHex(m_key.address().ref().cropped(0, 4)) << "Mode: " << (m_mode == NodeMode::PeerServer ? "PeerServer" : "Full");
+}
+
 PeerServer::PeerServer(std::string const& _clientVersion, BlockChain const& _ch, unsigned int _networkId, NodeMode _m):
 	m_clientVersion(_clientVersion),
 	m_mode(_m),
diff --git a/libethereum/PeerServer.h b/libethereum/PeerServer.h
index cc877300e..425f262a9 100644
--- a/libethereum/PeerServer.h
+++ b/libethereum/PeerServer.h
@@ -42,8 +42,11 @@ class PeerServer
 public:
 	/// Start server, listening for connections on the given port.
 	PeerServer(std::string const& _clientVersion, BlockChain const& _ch, unsigned int _networkId, unsigned short _port, NodeMode _m = NodeMode::Full, std::string const& _publicAddress = std::string(), bool _upnp = true);
+	/// Start server, listening for connections on a system-assigned port.
+	PeerServer(std::string const& _clientVersion, BlockChain const& _ch, unsigned int _networkId, NodeMode _m = NodeMode::Full, std::string const& _publicAddress = std::string(), bool _upnp = true);
 	/// Start server, but don't listen.
 	PeerServer(std::string const& _clientVersion, BlockChain const& _ch, unsigned int _networkId, NodeMode _m = NodeMode::Full);
+
 	~PeerServer();
 
 	static unsigned protocolVersion();
diff --git a/test/network.cpp b/test/network.cpp
new file mode 100644
index 000000000..3e27ac6b9
--- /dev/null
+++ b/test/network.cpp
@@ -0,0 +1,51 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	cpp-ethereum is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/** @file network.cpp
+ * @author Marko Simovic <markobarko@gmail.com>
+ * @date 2014
+ * Basic networking tests
+ */
+
+#include <boost/test/unit_test.hpp>
+#include <boost/filesystem/operations.hpp>
+#include <Client.h>
+#include <BlockChain.h>
+#include <PeerServer.h>
+#include "TestHelper.h"
+using namespace std;
+using namespace eth;
+
+BOOST_AUTO_TEST_CASE(listen_port_busy)
+{
+	short port = 20000;
+
+	//make use of the port ahead of our client
+	ba::io_service ioService;
+	bi::tcp::endpoint endPoint(bi::tcp::v4(), port);
+	bi::tcp::acceptor acceptor(ioService, endPoint);
+	acceptor.listen(10);
+
+	//prepare client and try to listen on same, used, port
+	Client c1("TestClient1", KeyPair::create().address(),
+			(boost::filesystem::temp_directory_path() / boost::filesystem::unique_path()).string());
+
+	c1.startNetwork(port);
+
+	BOOST_REQUIRE(c1.haveNetwork());
+	BOOST_REQUIRE(c1.peerServer()->listenPort() != 0);
+	BOOST_REQUIRE(c1.peerServer()->listenPort() != port);
+}