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add tcp reconnect when write failed #99

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add tcp reconnect when write failed #99

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24 changes: 14 additions & 10 deletions tcpclient.go
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Original file line number Diff line number Diff line change
Expand Up @@ -56,12 +56,13 @@ type tcpPackager struct {
}

// Encode adds modbus application protocol header:
// Transaction identifier: 2 bytes
// Protocol identifier: 2 bytes
// Length: 2 bytes
// Unit identifier: 1 byte
// Function code: 1 byte
// Data: n bytes
//
// Transaction identifier: 2 bytes
// Protocol identifier: 2 bytes
// Length: 2 bytes
// Unit identifier: 1 byte
// Function code: 1 byte
// Data: n bytes
func (mb *tcpPackager) Encode(pdu *ProtocolDataUnit) (adu []byte, err error) {
adu = make([]byte, tcpHeaderSize+1+len(pdu.Data))

Expand Down Expand Up @@ -107,10 +108,11 @@ func (mb *tcpPackager) Verify(aduRequest []byte, aduResponse []byte) (err error)
}

// Decode extracts PDU from TCP frame:
// Transaction identifier: 2 bytes
// Protocol identifier: 2 bytes
// Length: 2 bytes
// Unit identifier: 1 byte
//
// Transaction identifier: 2 bytes
// Protocol identifier: 2 bytes
// Length: 2 bytes
// Unit identifier: 1 byte
func (mb *tcpPackager) Decode(adu []byte) (pdu *ProtocolDataUnit, err error) {
// Read length value in the header
length := binary.BigEndian.Uint16(adu[4:])
Expand Down Expand Up @@ -167,6 +169,8 @@ func (mb *tcpTransporter) Send(aduRequest []byte) (aduResponse []byte, err error
// Send data
mb.logf("modbus: sending % x", aduRequest)
if _, err = mb.conn.Write(aduRequest); err != nil {
// Once an error occurs, set conn nil vai close() for the next request to reconnect
mb.close()
return
}
// Read header first
Expand Down