Added DialAssociation and ListenAssociation

These are helpers to easily run SCTP over UDP. Example adapted.
I added the Association postfix to keep space for a potential
Dial/Listen implementation that directly gives you a Stream.

Relates to #74

association.go

@@ -212,6 +212,19 @@ func Server(config Config) (*Association, error) {
 	}
 }
 
+// DialAssociation connects to the given network address and establishes a
+// SCTP association on top. The net.Conn in the config is ignored.
+func DialAssociation(network string, raddr *net.UDPAddr, config Config) (*Association, error) {
+	pConn, err := net.DialUDP(network, nil, raddr)
+	if err != nil {
+		return nil, err
+	}
+
+	config.NetConn = pConn
+
+	return Client(config)
+}
+
 // Client opens a SCTP stream over a conn
 func Client(config Config) (*Association, error) {
 	a := createAssociation(config)

examples/ping-pong/Makefile

@@ -1,7 +1,7 @@
 all: ping pong
 
-ping: ping.go conn.go
+ping: ping.go
 	go build -o $@
 
-pong: pong.go conn.go
+pong: pong.go
 	go build -o $@ -tags $@

examples/ping-pong/ping.go

@@ -12,18 +12,13 @@ import (
 )
 
 func main() {
-	conn, err := net.Dial("udp", "127.0.0.1:5678")
-	if err != nil {
-		log.Fatal(err)
-	}
-	defer conn.Close()
-	fmt.Println("dialed udp ponger")
+	// Prepare the IP to connect to
+	addr := &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: 5678}
 
 	config := sctp.Config{
-		NetConn:       conn,
 		LoggerFactory: logging.NewDefaultLoggerFactory(),
 	}
-	a, err := sctp.Client(config)
+	a, err := sctp.DialAssociation("udp", addr, config)
 	if err != nil {
 		log.Fatal(err)
 	}

examples/ping-pong/pong.go

@@ -13,29 +13,27 @@ import (
 )
 
 func main() {
-	addr := net.UDPAddr{
-		IP:   net.IPv4(127, 0, 0, 1),
-		Port: 5678,
-	}
+	addr := &net.UDPAddr{IP: net.IPv4(127, 0, 0, 1), Port: 5678}
 
-	conn, err := net.ListenUDP("udp", &addr)
+	config := sctp.Config{
+		LoggerFactory: logging.NewDefaultLoggerFactory(),
+	}
+	l, err := sctp.ListenAssociation("udp", addr, config)
 	if err != nil {
 		log.Fatal(err)
 	}
-	defer conn.Close()
-	fmt.Println("created a udp listener")
+	defer l.Close()
+	fmt.Println("created a listener")
 
-	config := sctp.Config{
-		NetConn:       &disconnectedPacketConn{pConn: conn},
-		LoggerFactory: logging.NewDefaultLoggerFactory(),
-	}
-	a, err := sctp.Server(config)
+	// Note: You should accept all incoming associations in a loop.
+	a, err := l.Accept()
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer a.Close()
-	fmt.Println("created a server")
+	fmt.Println("accepted an association")
 
+	// Note: You should accept all incoming streams in a loop.
 	stream, err := a.AcceptStream()
 	if err != nil {
 		log.Fatal(err)

go.mod

@@ -5,6 +5,7 @@ require (
 	github.com/kr/pretty v0.1.0 // indirect
 	github.com/pion/logging v0.2.2
 	github.com/pion/transport v0.10.0
+	github.com/pion/udp v0.1.0
 	github.com/pkg/errors v0.9.1
 	github.com/stretchr/testify v1.5.1
 	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect

go.sum

@@ -11,6 +11,8 @@ github.com/pion/logging v0.2.2 h1:M9+AIj/+pxNsDfAT64+MAVgJO0rsyLnoJKCqf//DoeY=
 github.com/pion/logging v0.2.2/go.mod h1:k0/tDVsRCX2Mb2ZEmTqNa7CWsQPc+YYCB7Q+5pahoms=
 github.com/pion/transport v0.10.0 h1:9M12BSneJm6ggGhJyWpDveFOstJsTiQjkLf4M44rm80=
 github.com/pion/transport v0.10.0/go.mod h1:BnHnUipd0rZQyTVB2SBGojFHT9CBt5C5TcsJSQGkvSE=
+github.com/pion/udp v0.1.0 h1:uGxQsNyrqG3GLINv36Ff60covYmfrLoxzwnCsIYspXI=
+github.com/pion/udp v0.1.0/go.mod h1:BPELIjbwE9PRbd/zxI/KYBnbo7B6+oA6YuEaNE8lths=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=

listener.go

@@ -0,0 +1,59 @@
+package sctp
+
+import (
+	"net"
+
+	"github.com/pion/udp"
+)
+
+// ListenAssociation creates a SCTP association listener
+func ListenAssociation(network string, laddr *net.UDPAddr, config Config) (*AssociationListener, error) {
+	lc := udp.ListenConfig{}
+	parent, err := lc.Listen(network, laddr)
+	if err != nil {
+		return nil, err
+	}
+	return &AssociationListener{
+		config: config,
+		parent: parent,
+	}, nil
+}
+
+// NewAssociationListener creates a SCTP association listener
+// which accepts connections from an inner Listener.
+// The net.Conn in the config is ignored.
+func NewAssociationListener(inner net.Listener, config Config) (*AssociationListener, error) {
+	return &AssociationListener{
+		config: config,
+		parent: inner,
+	}, nil
+}
+
+// AssociationListener represents a SCTP association listener
+type AssociationListener struct {
+	config Config
+	parent net.Listener
+}
+
+// Accept waits for and returns the next association to the listener.
+// You have to either close or read on all connection that are created.
+func (l *AssociationListener) Accept() (*Association, error) {
+	c, err := l.parent.Accept()
+	if err != nil {
+		return nil, err
+	}
+	l.config.NetConn = c
+	return Server(l.config)
+}
+
+// Close closes the listener.
+// Any blocked Accept operations will be unblocked and return errors.
+// Already Accepted connections are not closed.
+func (l *AssociationListener) Close() error {
+	return l.parent.Close()
+}
+
+// Addr returns the listener's network address.
+func (l *AssociationListener) Addr() net.Addr {
+	return l.parent.Addr()
+}