Add shortbuf erorr too

Cleanup the pull request a bit.

client.go

@@ -254,10 +254,10 @@ func (co *Conn) WriteMsg(m *Msg) (err error) {
 // Write implements the net.Conn Write method.
 func (co *Conn) Write(p []byte) (n int, err error) {
 	if t, ok := co.Conn.(*net.TCPConn); ok {
-		if len(p) < 2 {
+		lp := len(p)
+		if lp < 2 {
 			return 0, io.ErrShortBuffer
 		}
-		lp := len(p)
 		if lp > MaxMsgSize {
 			return 0, &Error{err: "message too large"}
 		}

server.go

@@ -414,6 +414,9 @@ func (w *response) Write(m []byte) (int, error) {
 		return n, err
 	case w.tcp != nil:
 		lm := len(m)
+		if lm < 2 {
+			return 0, io.ErrShortBuffer
+		}
 		if lm > MaxMsgSize {
 			return 0, &Error{err: "message too large"}
 		}