diff --git a/src/yggdrasil/tcp.go b/src/yggdrasil/tcp.go
index a190679f..c5654132 100644
--- a/src/yggdrasil/tcp.go
+++ b/src/yggdrasil/tcp.go
@@ -23,11 +23,14 @@ type tcpInterface struct {
 	serv  *net.TCPListener
 	mutex sync.Mutex // Protecting the below
 	calls map[string]struct{}
+	conns map[tcpInfo](chan struct{})
 }
 
-type tcpKeys struct {
-	box boxPubKey
-	sig sigPubKey
+type tcpInfo struct {
+	box        boxPubKey
+	sig        sigPubKey
+	localAddr  string // net.IPAddr.String(), not TCPAddr, don't care about port
+	remoteAddr string
 }
 
 func (iface *tcpInterface) init(core *Core, addr string) {
@@ -41,6 +44,7 @@ func (iface *tcpInterface) init(core *Core, addr string) {
 		panic(err)
 	}
 	iface.calls = make(map[string]struct{})
+	iface.conns = make(map[tcpInfo](chan struct{}))
 	go iface.listener()
 }
 
@@ -102,8 +106,8 @@ func (iface *tcpInterface) handler(sock *net.TCPConn) {
 	if n < len(keys) { /*panic("Partial key packet?") ;*/
 		return
 	}
-	ks := tcpKeys{}
-	if !tcp_chop_keys(&ks.box, &ks.sig, &keys) { /*panic("Invalid key packet?") ;*/
+	info := tcpInfo{}
+	if !tcp_chop_keys(&info.box, &info.sig, &keys) { /*panic("Invalid key packet?") ;*/
 		return
 	}
 	// Quit the parent call if this is a connection to ourself
@@ -115,16 +119,40 @@ func (iface *tcpInterface) handler(sock *net.TCPConn) {
 		}
 		return true
 	}
-	if equiv(ks.box[:], iface.core.boxPub[:]) {
+	if equiv(info.box[:], iface.core.boxPub[:]) {
 		return
 	} // testing
-	if equiv(ks.sig[:], iface.core.sigPub[:]) {
+	if equiv(info.sig[:], iface.core.sigPub[:]) {
 		return
 	}
+	// Check if we already have a connection to this node, close and block if yes
+	local := sock.LocalAddr().(*net.TCPAddr)
+	laddr := net.IPAddr{
+		IP:   local.IP,
+		Zone: local.Zone,
+	}
+	info.localAddr = laddr.String()
+	remote := sock.RemoteAddr().(*net.TCPAddr)
+	raddr := net.IPAddr{
+		IP:   remote.IP,
+		Zone: remote.Zone,
+	}
+	info.remoteAddr = raddr.String()
+	iface.mutex.Lock()
+	if blockChan, isIn := iface.conns[info]; isIn {
+		iface.mutex.Unlock()
+		sock.Close()
+		<-blockChan
+		return
+	}
+	blockChan := make(chan struct{})
+	iface.conns[info] = blockChan
+	iface.mutex.Unlock()
+	defer close(blockChan)
 	// Note that multiple connections to the same node are allowed
 	//  E.g. over different interfaces
 	linkIn := make(chan []byte, 1)
-	p := iface.core.peers.newPeer(&ks.box, &ks.sig) //, in, out)
+	p := iface.core.peers.newPeer(&info.box, &info.sig) //, in, out)
 	in := func(bs []byte) {
 		p.handlePacket(bs, linkIn)
 	}
@@ -197,8 +225,8 @@ func (iface *tcpInterface) handler(sock *net.TCPConn) {
 		p.core.peers.mutex.Unlock()
 		close(linkIn)
 	}()
-	them := sock.RemoteAddr()
-	themNodeID := getNodeID(&ks.box)
+	them := sock.RemoteAddr().(*net.TCPAddr)
+	themNodeID := getNodeID(&info.box)
 	themAddr := address_addrForNodeID(themNodeID)
 	themAddrString := net.IP(themAddr[:]).String()
 	themString := fmt.Sprintf("%s@%s", themAddrString, them)