diff --git a/src/pkg/net/ipraw_test.go b/src/pkg/net/ipraw_test.go
index 29d5984bdfe..43b02aef2ea 100644
--- a/src/pkg/net/ipraw_test.go
+++ b/src/pkg/net/ipraw_test.go
@@ -206,3 +206,33 @@ func parseICMPEchoReply(b []byte) (id, seqnum int) {
 	seqnum = int(b[6])<<8 | int(b[7])
 	return
 }
+
+var ipConnLocalNameTests = []struct {
+	net   string
+	laddr *IPAddr
+}{
+	{"ip4:icmp", &IPAddr{IP: IPv4(127, 0, 0, 1)}},
+	{"ip4:icmp", &IPAddr{}},
+	{"ip4:icmp", nil},
+}
+
+func TestIPConnLocalName(t *testing.T) {
+	if os.Getuid() != 0 {
+		t.Logf("skipping test; must be root")
+		return
+	}
+
+	for _, tt := range ipConnLocalNameTests {
+		c, err := ListenIP(tt.net, tt.laddr)
+		if err != nil {
+			t.Errorf("ListenIP failed: %v", err)
+			return
+		}
+		defer c.Close()
+		la := c.LocalAddr()
+		if la == nil {
+			t.Error("IPConn.LocalAddr failed")
+			return
+		}
+	}
+}
diff --git a/src/pkg/net/iprawsock_posix.go b/src/pkg/net/iprawsock_posix.go
index 4d8b5341d97..00e87cfbf0d 100644
--- a/src/pkg/net/iprawsock_posix.go
+++ b/src/pkg/net/iprawsock_posix.go
@@ -175,7 +175,7 @@ func dialIP(netProto string, laddr, raddr *IPAddr, deadline time.Time) (*IPConn,
 	switch net {
 	case "ip", "ip4", "ip6":
 	default:
-		return nil, UnknownNetworkError(net)
+		return nil, UnknownNetworkError(netProto)
 	}
 	if raddr == nil {
 		return nil, &OpError{"dial", netProto, nil, errMissingAddress}
@@ -199,7 +199,7 @@ func ListenIP(netProto string, laddr *IPAddr) (*IPConn, error) {
 	switch net {
 	case "ip", "ip4", "ip6":
 	default:
-		return nil, UnknownNetworkError(net)
+		return nil, UnknownNetworkError(netProto)
 	}
 	fd, err := internetSocket(net, laddr.toAddr(), nil, noDeadline, syscall.SOCK_RAW, proto, "listen", sockaddrToIP)
 	if err != nil {
diff --git a/src/pkg/net/tcp_test.go b/src/pkg/net/tcp_test.go
index 53daf5b0999..f6e4df30a8b 100644
--- a/src/pkg/net/tcp_test.go
+++ b/src/pkg/net/tcp_test.go
@@ -116,3 +116,33 @@ func benchmarkTCP(b *testing.B, persistent, timeout bool) {
 		sem <- true
 	}
 }
+
+var tcpListenerNameTests = []struct {
+	net   string
+	laddr *TCPAddr
+}{
+	{"tcp4", &TCPAddr{IP: IPv4(127, 0, 0, 1)}},
+	{"tcp4", &TCPAddr{}},
+	{"tcp4", nil},
+}
+
+func TestTCPListenerName(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Logf("skipping test to avoid external network")
+		return
+	}
+
+	for _, tt := range tcpListenerNameTests {
+		ln, err := ListenTCP(tt.net, tt.laddr)
+		if err != nil {
+			t.Errorf("ListenTCP failed: %v", err)
+			return
+		}
+		defer ln.Close()
+		la := ln.Addr()
+		if a, ok := la.(*TCPAddr); !ok || a.Port == 0 {
+			t.Errorf("got %v; expected a proper address with non-zero port number", la)
+			return
+		}
+	}
+}
diff --git a/src/pkg/net/tcpsock_plan9.go b/src/pkg/net/tcpsock_plan9.go
index a77633b355e..d4d39e80f4a 100644
--- a/src/pkg/net/tcpsock_plan9.go
+++ b/src/pkg/net/tcpsock_plan9.go
@@ -89,7 +89,7 @@ func ListenTCP(net string, laddr *TCPAddr) (l *TCPListener, err error) {
 		return nil, UnknownNetworkError(net)
 	}
 	if laddr == nil {
-		return nil, &OpError{"listen", net, nil, errMissingAddress}
+		laddr = &TCPAddr{}
 	}
 	l1, err := listenPlan9(net, laddr)
 	if err != nil {
diff --git a/src/pkg/net/tcpsock_posix.go b/src/pkg/net/tcpsock_posix.go
index 09654a4b580..7b827f1e971 100644
--- a/src/pkg/net/tcpsock_posix.go
+++ b/src/pkg/net/tcpsock_posix.go
@@ -143,14 +143,18 @@ func (c *TCPConn) SetNoDelay(noDelay bool) error {
 // which must be "tcp", "tcp4", or "tcp6".  If laddr is not nil, it is used
 // as the local address for the connection.
 func DialTCP(net string, laddr, raddr *TCPAddr) (*TCPConn, error) {
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+	if raddr == nil {
+		return nil, &OpError{"dial", net, nil, errMissingAddress}
+	}
 	return dialTCP(net, laddr, raddr, noDeadline)
 }
 
 func dialTCP(net string, laddr, raddr *TCPAddr, deadline time.Time) (*TCPConn, error) {
-	if raddr == nil {
-		return nil, &OpError{"dial", net, nil, errMissingAddress}
-	}
-
 	fd, err := internetSocket(net, laddr.toAddr(), raddr.toAddr(), deadline, syscall.SOCK_STREAM, 0, "dial", sockaddrToTCP)
 
 	// TCP has a rarely used mechanism called a 'simultaneous connection' in
@@ -224,25 +228,6 @@ type TCPListener struct {
 	fd *netFD
 }
 
-// ListenTCP announces on the TCP address laddr and returns a TCP listener.
-// Net must be "tcp", "tcp4", or "tcp6".
-// If laddr has a port of 0, it means to listen on some available port.
-// The caller can use l.Addr() to retrieve the chosen address.
-func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error) {
-	fd, err := internetSocket(net, laddr.toAddr(), nil, noDeadline, syscall.SOCK_STREAM, 0, "listen", sockaddrToTCP)
-	if err != nil {
-		return nil, err
-	}
-	err = syscall.Listen(fd.sysfd, listenerBacklog)
-	if err != nil {
-		closesocket(fd.sysfd)
-		return nil, &OpError{"listen", net, laddr, err}
-	}
-	l := new(TCPListener)
-	l.fd = fd
-	return l, nil
-}
-
 // AcceptTCP accepts the next incoming call and returns the new connection
 // and the remote address.
 func (l *TCPListener) AcceptTCP() (c *TCPConn, err error) {
@@ -291,3 +276,30 @@ func (l *TCPListener) SetDeadline(t time.Time) error {
 // It is the caller's responsibility to close f when finished.
 // Closing l does not affect f, and closing f does not affect l.
 func (l *TCPListener) File() (f *os.File, err error) { return l.fd.dup() }
+
+// ListenTCP announces on the TCP address laddr and returns a TCP listener.
+// Net must be "tcp", "tcp4", or "tcp6".
+// If laddr has a port of 0, it means to listen on some available port.
+// The caller can use l.Addr() to retrieve the chosen address.
+func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error) {
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+	if laddr == nil {
+		laddr = &TCPAddr{}
+	}
+	fd, err := internetSocket(net, laddr.toAddr(), nil, noDeadline, syscall.SOCK_STREAM, 0, "listen", sockaddrToTCP)
+	if err != nil {
+		return nil, err
+	}
+	err = syscall.Listen(fd.sysfd, listenerBacklog)
+	if err != nil {
+		closesocket(fd.sysfd)
+		return nil, &OpError{"listen", net, laddr, err}
+	}
+	l := new(TCPListener)
+	l.fd = fd
+	return l, nil
+}
diff --git a/src/pkg/net/udp_test.go b/src/pkg/net/udp_test.go
index f80d3b5a9cf..37b904f3242 100644
--- a/src/pkg/net/udp_test.go
+++ b/src/pkg/net/udp_test.go
@@ -87,3 +87,33 @@ func testWriteToPacketConn(t *testing.T, raddr string) {
 		t.Fatal("Write should fail")
 	}
 }
+
+var udpConnLocalNameTests = []struct {
+	net   string
+	laddr *UDPAddr
+}{
+	{"udp4", &UDPAddr{IP: IPv4(127, 0, 0, 1)}},
+	{"udp4", &UDPAddr{}},
+	{"udp4", nil},
+}
+
+func TestUDPConnLocalName(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Logf("skipping test to avoid external network")
+		return
+	}
+
+	for _, tt := range udpConnLocalNameTests {
+		c, err := ListenUDP(tt.net, tt.laddr)
+		if err != nil {
+			t.Errorf("ListenUDP failed: %v", err)
+			return
+		}
+		defer c.Close()
+		la := c.LocalAddr()
+		if a, ok := la.(*UDPAddr); !ok || a.Port == 0 {
+			t.Errorf("got %v; expected a proper address with non-zero port number", la)
+			return
+		}
+	}
+}
diff --git a/src/pkg/net/udpsock_plan9.go b/src/pkg/net/udpsock_plan9.go
index c04660baa27..767a421cba4 100644
--- a/src/pkg/net/udpsock_plan9.go
+++ b/src/pkg/net/udpsock_plan9.go
@@ -184,7 +184,7 @@ func ListenUDP(net string, laddr *UDPAddr) (c *UDPConn, err error) {
 		return nil, UnknownNetworkError(net)
 	}
 	if laddr == nil {
-		return nil, &OpError{"listen", net, nil, errMissingAddress}
+		laddr = &UDPAddr{}
 	}
 	l, err := listenPlan9(net, laddr)
 	if err != nil {
diff --git a/src/pkg/net/udpsock_posix.go b/src/pkg/net/udpsock_posix.go
index f6e2c17c3cb..d7329bf32fc 100644
--- a/src/pkg/net/udpsock_posix.go
+++ b/src/pkg/net/udpsock_posix.go
@@ -193,7 +193,7 @@ func ListenUDP(net string, laddr *UDPAddr) (*UDPConn, error) {
 		return nil, UnknownNetworkError(net)
 	}
 	if laddr == nil {
-		return nil, &OpError{"listen", net, nil, errMissingAddress}
+		laddr = &UDPAddr{}
 	}
 	fd, err := internetSocket(net, laddr.toAddr(), nil, noDeadline, syscall.SOCK_DGRAM, 0, "listen", sockaddrToUDP)
 	if err != nil {