Add transport interface and its UDP implementation

transport/conn.go

@@ -0,0 +1,21 @@
+package transport
+
+import "net"
+
+// Conn represents a generic network connection.
+type Conn interface {
+	// Read reads data from the connection.
+	Read(b []byte) (n int, err error)
+
+	// Write writes data to the connection.
+	Write(b []byte) (n int, err error)
+
+	// Close closes the connection.
+	Close() error
+
+	// LocalAddr returns the local network address.
+	LocalAddr() net.Addr
+
+	// RemoteAddr returns the remote network address.
+	RemoteAddr() net.Addr
+}

transport/udp/udp.go

@@ -0,0 +1,61 @@
+// Package udp provides transport over UDP.
+package udp
+
+import "net"
+
+// Conn implements the transport.Conn interface for UDP.
+type Conn struct {
+	localAddr  *net.UDPAddr
+	remoteAddr *net.UDPAddr
+	*net.UDPConn
+}
+
+// New creates a connection with the remote peer over UDP.
+func New(local, remote string) (*Conn, error) {
+	localAddr, err := net.ResolveUDPAddr("udp", local)
+	if nil != err {
+		return nil, err
+	}
+
+	remoteAddr, err := net.ResolveUDPAddr("udp", remote)
+	if nil != err {
+		return nil, err
+	}
+
+	conn, err := net.ListenUDP("udp", localAddr)
+	if nil != err {
+		return nil, err
+	}
+
+	return &Conn{localAddr, remoteAddr, conn}, nil
+}
+
+// Read reads data from the peer.
+func (c *Conn) Read(b []byte) (int, error) {
+	n, addr, err := c.ReadFromUDP(b)
+	if err != nil {
+		return n, err
+	}
+
+	// Discard packets not from the peer
+	if addr.String() != c.remoteAddr.String() {
+		return 0, nil
+	}
+
+	return n, err
+}
+
+// Write writes data to the peer.
+func (c *Conn) Write(b []byte) (int, error) {
+	return c.WriteToUDP(b, c.remoteAddr)
+}
+
+// LocalAddr returns the local network address.
+func (c *Conn) LocalAddr() net.Addr {
+	return c.localAddr
+}
+
+// RemoteAddr returns the remote network address.
+func (c *Conn) RemoteAddr() net.Addr {
+	return c.remoteAddr
+}