client.go      |  1 +
 client_test.go |  9 +++++----
 config.go      |  3 ++-
 portfwd.go     | 41 +++++++++++++++++++++++++++++++++++++++++

diff --git a/client.go b/client.go
index fba0b1e22e020ee95298ffaf05b7c701d2e77cab..ab2fe08d9fc8866b82f93e3c466e9422d42027e9 100644
--- a/client.go
+++ b/client.go
@@ -303,6 +303,7 @@ 		cl.config.ListenAddr)
 	if err != nil {
 		return
 	}
+	go cl.forwardPort()
 	if cl.tcpListener != nil {
 		go cl.acceptConnections(cl.tcpListener, false)
 	}
diff --git a/client_test.go b/client_test.go
index 13c6cbddd9811742be45e71786fe69d48119ed11..51f8ad4b70bf951daca7ad1f583470637ea39844 100644
--- a/client_test.go
+++ b/client_test.go
@@ -33,10 +33,11 @@ )
 
 func TestingConfig() *Config {
 	return &Config{
-		ListenAddr:      "localhost:0",
-		NoDHT:           true,
-		DataDir:         tempDir(),
-		DisableTrackers: true,
+		ListenAddr:              "localhost:0",
+		NoDHT:                   true,
+		DataDir:                 tempDir(),
+		DisableTrackers:         true,
+		NoDefaultPortForwarding: true,
 		// Debug:           true,
 	}
 }
diff --git a/config.go b/config.go
index cb597b200c7df7b38b9105891a97dc27a639f45e..a8933abaaaeca943cfe55d98a3ea03d55d2b64aa 100644
--- a/config.go
+++ b/config.go
@@ -33,7 +33,8 @@ 	DataDir string `long:"data-dir" description:"directory to store downloaded torrent data"`
 	// The address to listen for new uTP and TCP bittorrent protocol
 	// connections. DHT shares a UDP socket with uTP unless configured
 	// otherwise.
-	ListenAddr string `long:"listen-addr" value-name:"HOST:PORT"`
+	ListenAddr              string `long:"listen-addr" value-name:"HOST:PORT"`
+	NoDefaultPortForwarding bool
 	// Don't announce to trackers. This only leaves DHT to discover peers.
 	DisableTrackers bool `long:"disable-trackers"`
 	DisablePEX      bool `long:"disable-pex"`
diff --git a/portfwd.go b/portfwd.go
new file mode 100644
index 0000000000000000000000000000000000000000..1f1ecd58095081d016efabc2b8097c9f5019f2f1
--- /dev/null
+++ b/portfwd.go
@@ -0,0 +1,41 @@
+package torrent
+
+import (
+	"log"
+	"time"
+
+	flog "github.com/anacrolix/log"
+
+	"github.com/syncthing/syncthing/lib/nat"
+	"github.com/syncthing/syncthing/lib/upnp"
+)
+
+func addPortMapping(d nat.Device, proto nat.Protocol, internalPort int, debug bool) {
+	externalPort, err := d.AddPortMapping(proto, internalPort, internalPort, "anacrolix/torrent", 0)
+	if err != nil {
+		log.Printf("error adding %s port mapping: %s", proto, err)
+	} else if externalPort != internalPort {
+		log.Printf("external port %d does not match internal port %d in port mapping", externalPort, internalPort)
+	} else if debug {
+		log.Printf("forwarded external %s port %d", proto, externalPort)
+	}
+}
+
+func (cl *Client) forwardPort() {
+	cl.mu.Lock()
+	defer cl.mu.Unlock()
+	if cl.config.NoDefaultPortForwarding {
+		return
+	}
+	cl.mu.Unlock()
+	ds := upnp.Discover(0, 2*time.Second)
+	cl.mu.Lock()
+	flog.Default.Emit(flog.Fmsg("discovered %d upnp devices", len(ds)))
+	port := cl.incomingPeerPort()
+	cl.mu.Unlock()
+	for _, d := range ds {
+		go addPortMapping(d, nat.TCP, port, cl.config.Debug)
+		go addPortMapping(d, nat.UDP, port, cl.config.Debug)
+	}
+	cl.mu.Lock()
+}