Improve error messages, close conn on transactionID mismatch.

client.go

@@ -76,6 +76,7 @@ func (m *Mbclient) ReadRegisters(first uint16, numRegs uint16) ([]uint16, error)
 	binary.BigEndian.PutUint16(req[8:10], first-1)
 	binary.BigEndian.PutUint16(req[10:12], numRegs)
 	m.conn.SetDeadline(time.Now().Add(5 * time.Second))
+	fmt.Printf("%x", req)
 	byteswritten, err := m.conn.Write(req)
 	if err != nil {
 		m.closeConn()
@@ -95,7 +96,7 @@ func (m *Mbclient) ReadRegisters(first uint16, numRegs uint16) ([]uint16, error)
 	expectedDataLength := responseHeader.length - 1
 
 	if m.transactionCounter != responseHeader.transactionID {
-		m.t.Reset(0)
+		m.closeConn()
 		return nil, fmt.Errorf("modbus transaction mismatch %v != %v", m.transactionCounter, responseHeader.transactionID)
 	}
 	response := make([]byte, expectedDataLength)
@@ -112,7 +113,7 @@ func (m *Mbclient) ReadRegisters(first uint16, numRegs uint16) ([]uint16, error)
 	err = mbpayload.unMarshal(response)
 	if mbpayload.functionCode != 3 {
 		m.t.Reset(m.keepAliveDuration)
-		return nil, fmt.Errorf("modbus exception %v req: %v", mbpayload.functionCode&0x7F, req)
+		return nil, fmt.Errorf("modbus exception %v req: %x", mbpayload.functionCode&0x7F, req)
 	}
 	if err != nil {
 		m.t.Reset(m.keepAliveDuration)