Add UDP transport with picomap port 28781, info -udp flag

lib/client/udp.go

@@ -0,0 +1,55 @@
+package client
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net"
+	"time"
+)
+
+const PicomapPort = 28781
+
+type udpTransport struct {
+	conn *net.UDPConn
+	buf  bytes.Buffer
+}
+
+func NewUDP(addr string, timeout time.Duration) (*Client, error) {
+	raddr, err := net.ResolveUDPAddr("udp4", fmt.Sprintf("%s:%d", addr, PicomapPort))
+	if err != nil {
+		return nil, fmt.Errorf("resolve %s: %w", addr, err)
+	}
+	conn, err := net.DialUDP("udp4", nil, raddr)
+	if err != nil {
+		return nil, fmt.Errorf("dial %s: %w", addr, err)
+	}
+	return &Client{transport: &udpTransport{conn: conn}, timeout: timeout}, nil
+}
+
+func (t *udpTransport) Send(data []byte) error {
+	_, err := t.conn.Write(data)
+	return err
+}
+
+func (t *udpTransport) SetReadTimeout(timeout time.Duration) {
+	t.conn.SetReadDeadline(time.Now().Add(timeout))
+}
+
+func (t *udpTransport) Reader() io.Reader {
+	for {
+		if t.buf.Len() > 0 {
+			return &t.buf
+		}
+		pkt := make([]byte, 1500)
+		n, err := t.conn.Read(pkt)
+		if err != nil {
+			return &t.buf
+		}
+		t.buf.Write(pkt[:n])
+	}
+}
+
+func (t *udpTransport) Close() error {
+	return t.conn.Close()
+}