add tunnel handler and connector

handler/tunnel/conn.go

@@ -0,0 +1,26 @@
+package tunnel
+
+import (
+	"bytes"
+	"net"
+)
+
+type tcpConn struct {
+	net.Conn
+	wbuf bytes.Buffer
+}
+
+func (c *tcpConn) Read(b []byte) (n int, err error) {
+	return c.Conn.Read(b)
+}
+
+func (c *tcpConn) Write(b []byte) (n int, err error) {
+	n = len(b) // force byte length consistent
+	if c.wbuf.Len() > 0 {
+		c.wbuf.Write(b) // append the data to the cached header
+		_, err = c.wbuf.WriteTo(c.Conn)
+		return
+	}
+	_, err = c.Conn.Write(b)
+	return
+}