Use system-assigned epheral ports

Added createConnectedUDPConnPair().
Relates to #270

association_test.go

@@ -2570,22 +2570,25 @@ func TestAssocMaxMessageSize(t *testing.T) {
 	})
 }
 
-func createAssocs() (*Association, *Association, error) {
-	addr1 := &net.UDPAddr{
-		IP:   net.IP{127, 0, 0, 1},
-		Port: 1234,
+// crateUDPConnPair creates a pair of net.UDPConn objects that are connected with each other
+func createUDPConnPair(t *testing.T) (*net.UDPConn, *net.UDPConn, error) {
+	udp1, err := net.ListenUDP("udp", &net.UDPAddr{IP: net.ParseIP("127.0.0.1")})
+	if err != nil {
+		return nil, nil, err
 	}
+	addr1, ok := udp1.LocalAddr().(*net.UDPAddr)
+	require.True(t, ok)
+	err = udp1.Close()
+	require.NoError(t, err)
 
-	addr2 := &net.UDPAddr{
-		IP:   net.IP{127, 0, 0, 1},
-		Port: 5678,
+	udp2, err := net.ListenUDP("udp", &net.UDPAddr{IP: net.ParseIP("127.0.0.1")})
+	if err != nil {
+		return nil, nil, err
 	}
-
-	var udp1 *net.UDPConn
-	var udp2 *net.UDPConn
-	var a1 *Association
-	var a2 *Association
-	var err error
+	addr2, ok := udp2.LocalAddr().(*net.UDPAddr)
+	require.True(t, ok)
+	err = udp2.Close()
+	require.NoError(t, err)
 
 	udp1, err = net.DialUDP("udp", addr1, addr2)
 	if err != nil {
@@ -2597,14 +2600,24 @@ func createAssocs() (*Association, *Association, error) {
 		return nil, nil, err
 	}
 
+	return udp1, udp2, nil
+}
+
+func createAssocs(t *testing.T) (*Association, *Association, error) {
+	udp1, udp2, err := createUDPConnPair(t)
+	if err != nil {
+		return nil, nil, err
+	}
+
 	loggerFactory := logging.NewDefaultLoggerFactory()
 
 	a1Chan := make(chan interface{})
 	a2Chan := make(chan interface{})
 
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
 	go func() {
-		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
-		defer cancel()
 		a, err2 := createClientWithContext(ctx, Config{
 			NetConn:       udp1,
 			LoggerFactory: loggerFactory,
@@ -2617,8 +2630,6 @@ func createAssocs() (*Association, *Association, error) {
 	}()
 
 	go func() {
-		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
-		defer cancel()
 		a, err2 := createClientWithContext(ctx, Config{
 			NetConn:       udp2,
 			LoggerFactory: loggerFactory,
@@ -2630,6 +2641,9 @@ func createAssocs() (*Association, *Association, error) {
 		}
 	}()
 
+	var a1 *Association
+	var a2 *Association
+
 loop:
 	for {
 		select {
@@ -2667,7 +2681,7 @@ func TestAssociation_Shutdown(t *testing.T) {
 		assert.Equal(t, n0, runtime.NumGoroutine(), "goroutine is leaked")
 	}()
 
-	a1, a2, err := createAssocs()
+	a1, a2, err := createAssocs(t)
 	require.NoError(t, err)
 
 	s11, err := a1.OpenStream(1, PayloadTypeWebRTCString)
@@ -2711,7 +2725,7 @@ func TestAssociation_ShutdownDuringWrite(t *testing.T) {
 		assert.Equal(t, n0, runtime.NumGoroutine(), "goroutine is leaked")
 	}()
 
-	a1, a2, err := createAssocs()
+	a1, a2, err := createAssocs(t)
 	require.NoError(t, err)
 
 	s11, err := a1.OpenStream(1, PayloadTypeWebRTCString)
@@ -2928,7 +2942,7 @@ func TestAssociation_Abort(t *testing.T) {
 		assert.Equal(t, n0, runtime.NumGoroutine(), "goroutine is leaked")
 	}()
 
-	a1, a2, err := createAssocs()
+	a1, a2, err := createAssocs(t)
 	require.NoError(t, err)
 
 	s11, err := a1.OpenStream(1, PayloadTypeWebRTCString)