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tcpclient.go
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tcpclient.go
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package modbus
import (
"encoding/binary"
"fmt"
"io"
"net"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/goburrow/serial"
)
const (
// TCPDefaultTimeout TCP Default timeout
TCPDefaultTimeout = 1 * time.Second
// TCPDefaultAutoReconnect TCP Default auto reconnect count
TCPDefaultAutoReconnect = 1
)
// TCPClientProvider implements ClientProvider interface.
type TCPClientProvider struct {
logger
address string
mu sync.Mutex
// TCP connection
conn net.Conn
// Connect & Read timeout
timeout time.Duration
// if > 0, when disconnect,it will try to reconnect the remote
// but if we active close self,it will not to reconnect
// if == 0 auto reconnect not active
autoReconnect byte
// For synchronization between messages of server & client
transactionID uint32
// request
*pool
}
// check TCPClientProvider implements the interface ClientProvider underlying method
var _ ClientProvider = (*TCPClientProvider)(nil)
// request pool, all TCP client use this pool
var tcpPool = newPool(tcpAduMaxSize)
// NewTCPClientProvider allocates a new TCPClientProvider.
func NewTCPClientProvider(address string, opts ...ClientProviderOption) *TCPClientProvider {
p := &TCPClientProvider{
address: address,
timeout: TCPDefaultTimeout,
autoReconnect: TCPDefaultAutoReconnect,
pool: tcpPool,
logger: newLogger("modbusTCPMaster =>"),
}
for _, opt := range opts {
opt(p)
}
return p
}
// encode modbus application protocol header & pdu to TCP frame,return adu.
// ---- MBAP header ----
// Transaction identifier: 2 bytes
// Protocol identifier: 2 bytes
// Length: 2 bytes
// Unit identifier: 1 byte
// ---- data Unit ----
// Function code: 1 byte
// Data: n bytes
func (sf *protocolFrame) encodeTCPFrame(tid uint16, slaveID byte,
pdu ProtocolDataUnit) (protocolTCPHeader, []byte, error) {
length := tcpHeaderMbapSize + 1 + len(pdu.Data)
if length > tcpAduMaxSize {
return protocolTCPHeader{}, nil, fmt.Errorf("modbus: length of data '%v' must not be bigger than '%v'",
length, tcpAduMaxSize)
}
head := protocolTCPHeader{
tid,
tcpProtocolIdentifier,
uint16(2 + len(pdu.Data)), // sizeof(SlaveId) + sizeof(FuncCode) + Data
slaveID,
}
// fill adu buffer
adu := sf.adu[0:length]
binary.BigEndian.PutUint16(adu, head.transactionID) // MBAP Transaction identifier
binary.BigEndian.PutUint16(adu[2:], head.protocolID) // MBAP Protocol identifier
binary.BigEndian.PutUint16(adu[4:], head.length) // MBAP Length
adu[6] = head.slaveID // MBAP Unit identifier
adu[tcpHeaderMbapSize] = pdu.FuncCode // PDU funcCode
copy(adu[tcpHeaderMbapSize+1:], pdu.Data) // PDU data
return head, adu, nil
}
// decode extracts tcpHeader & PDU from TCP frame:
// ---- MBAP header ----
// Transaction identifier: 2 bytes
// Protocol identifier: 2 bytes
// Length: 2 bytes
// Unit identifier: 1 byte
// ---- data Unit ----
// Function : 1 byte
// Data : 0 up to 252 bytes
func decodeTCPFrame(adu []byte) (protocolTCPHeader, []byte, error) {
if len(adu) < tcpAduMinSize { // Minimum size (including MBAP, funcCode)
return protocolTCPHeader{}, nil, fmt.Errorf("modbus: response length '%v' does not meet minimum '%v'",
len(adu), tcpAduMinSize)
}
// Read length value in the header
head := protocolTCPHeader{
transactionID: binary.BigEndian.Uint16(adu),
protocolID: binary.BigEndian.Uint16(adu[2:]),
length: binary.BigEndian.Uint16(adu[4:]),
slaveID: adu[6],
}
pduLength := len(adu) - tcpHeaderMbapSize
if pduLength != int(head.length-1) {
return head, nil, fmt.Errorf("modbus: length in response '%v' does not match pdu data length '%v'",
head.length-1, pduLength)
}
// The first byte after header is function code
return head, adu[tcpHeaderMbapSize:], nil
}
// verify confirms valid data
func verifyTCPFrame(reqHead, rspHead protocolTCPHeader, reqPDU, rspPDU ProtocolDataUnit) error {
switch {
case rspHead.transactionID != reqHead.transactionID: // Check transaction ID
return fmt.Errorf("modbus: response transaction id '%v' does not match request '%v'",
rspHead.transactionID, reqHead.transactionID)
case rspHead.protocolID != reqHead.protocolID: // Check protocol ID
return fmt.Errorf("modbus: response protocol id '%v' does not match request '%v'",
rspHead.protocolID, reqHead.protocolID)
case rspHead.slaveID != reqHead.slaveID: // Check slaveID same
return fmt.Errorf("modbus: response unit id '%v' does not match request '%v'",
rspHead.slaveID, reqHead.slaveID)
case rspPDU.FuncCode != reqPDU.FuncCode: // Check correct function code returned (exception)
return responseError(rspPDU)
case rspPDU.Data == nil || len(rspPDU.Data) == 0: // check Empty response
return fmt.Errorf("modbus: response data is empty")
}
return nil
}
// Send the request to tcp and get the response
func (sf *TCPClientProvider) Send(slaveID byte, request ProtocolDataUnit) (ProtocolDataUnit, error) {
var response ProtocolDataUnit
frame := sf.pool.get()
defer sf.pool.put(frame)
// add transaction id
tid := uint16(atomic.AddUint32(&sf.transactionID, 1))
head, aduRequest, err := frame.encodeTCPFrame(tid, slaveID, request)
if err != nil {
return response, err
}
aduResponse, err := sf.SendRawFrame(aduRequest)
if err != nil {
return response, err
}
rspHead, pdu, err := decodeTCPFrame(aduResponse)
if err != nil {
return response, err
}
response = ProtocolDataUnit{pdu[0], pdu[1:]}
err = verifyTCPFrame(head, rspHead, request, response)
return response, err
}
// SendPdu send pdu request to the remote server
func (sf *TCPClientProvider) SendPdu(slaveID byte, pduRequest []byte) ([]byte, error) {
if len(pduRequest) < pduMinSize || len(pduRequest) > pduMaxSize {
return nil, fmt.Errorf("modbus: rspPdu size '%v' must not be between '%v' and '%v'",
len(pduRequest), pduMinSize, pduMaxSize)
}
frame := sf.pool.get()
defer sf.pool.put(frame)
// add transaction id
tid := uint16(atomic.AddUint32(&sf.transactionID, 1))
request := ProtocolDataUnit{pduRequest[0], pduRequest[1:]}
head, aduRequest, err := frame.encodeTCPFrame(tid, slaveID, request)
if err != nil {
return nil, err
}
aduResponse, err := sf.SendRawFrame(aduRequest)
if err != nil {
return nil, err
}
rspHead, rspPdu, err := decodeTCPFrame(aduResponse)
if err != nil {
return nil, err
}
response := ProtocolDataUnit{rspPdu[0], rspPdu[1:]}
if err = verifyTCPFrame(head, rspHead, request, response); err != nil {
return nil, err
}
// rspPdu pass tcpMBAP head
return rspPdu, nil
}
// SendRawFrame send raw adu request frame
func (sf *TCPClientProvider) SendRawFrame(aduRequest []byte) (aduResponse []byte, err error) {
sf.mu.Lock()
defer sf.mu.Unlock()
if !sf.isConnected() {
return nil, ErrClosedConnection
}
// Send data
sf.Debug("sending [% x]", aduRequest)
// Set write and read timeout
var timeout time.Time
var tryCnt byte
for {
if sf.timeout > 0 {
timeout = time.Now().Add(sf.timeout)
}
if err = sf.conn.SetDeadline(timeout); err != nil {
return nil, err
}
if _, err = sf.conn.Write(aduRequest); err == nil { // success
break
}
if sf.autoReconnect == 0 {
return
}
for {
err = sf.connect()
if err == nil {
break
}
tryCnt++
if tryCnt >= sf.autoReconnect {
return
}
}
}
// Read header first
var data [tcpAduMaxSize]byte
var cnt int
var mErr error
for {
if sf.timeout > 0 {
timeout = time.Now().Add(sf.timeout)
}
if err = sf.conn.SetDeadline(timeout); err != nil {
return nil, err
}
if cnt, err = io.ReadFull(sf.conn, data[:tcpHeaderMbapSize]); err == nil {
break
}
if sf.autoReconnect == 0 {
return
}
mErr = err
if e, ok := err.(net.Error); ok && !e.Temporary() ||
err != io.EOF && err != io.ErrClosedPipe ||
strings.Contains(err.Error(), "use of closed network connection") ||
cnt == 0 && err == io.EOF {
for {
err = sf.connect()
if err == nil {
break
}
tryCnt++
if tryCnt >= sf.autoReconnect {
return
}
}
}
tryCnt++
if tryCnt >= sf.autoReconnect {
err = mErr
return
}
}
// Read length, ignore transaction & protocol id (4 bytes)
length := int(binary.BigEndian.Uint16(data[4:]))
switch {
case length <= 0:
_ = sf.flush(data[:])
err = fmt.Errorf("modbus: length in response header '%v' must not be zero", length)
return
case length > (tcpAduMaxSize - (tcpHeaderMbapSize - 1)):
_ = sf.flush(data[:])
err = fmt.Errorf("modbus: length in response header '%v' must not greater than '%v'",
length, tcpAduMaxSize-tcpHeaderMbapSize+1)
return
}
if sf.timeout > 0 {
timeout = time.Now().Add(sf.timeout)
}
if err = sf.conn.SetDeadline(timeout); err != nil {
return nil, err
}
// Skip unit id
length += tcpHeaderMbapSize - 1
if _, err = io.ReadFull(sf.conn, data[tcpHeaderMbapSize:length]); err != nil {
return
}
aduResponse = data[:length]
sf.Debug("received [% x]", aduResponse)
return aduResponse, nil
}
// Connect establishes a new connection to the address in Address.
// Connect and Close are exported so that multiple requests can be done with one session
func (sf *TCPClientProvider) Connect() error {
sf.mu.Lock()
err := sf.connect()
sf.mu.Unlock()
return err
}
// Caller must hold the mutex before calling this method.
func (sf *TCPClientProvider) connect() error {
dialer := &net.Dialer{Timeout: sf.timeout}
conn, err := dialer.Dial("tcp", sf.address)
if err != nil {
return err
}
sf.conn = conn
return nil
}
// IsConnected returns a bool signifying whether
// the client is connected or not.
func (sf *TCPClientProvider) IsConnected() bool {
sf.mu.Lock()
b := sf.isConnected()
sf.mu.Unlock()
return b
}
// Caller must hold the mutex before calling this method.
func (sf *TCPClientProvider) isConnected() bool {
return sf.conn != nil
}
// SetAutoReconnect set auto reconnect retry count
func (sf *TCPClientProvider) SetAutoReconnect(cnt byte) {
sf.mu.Lock()
sf.autoReconnect = cnt
if sf.autoReconnect > 6 {
sf.autoReconnect = 6
}
sf.mu.Unlock()
}
// Close closes current connection.
func (sf *TCPClientProvider) Close() (err error) {
sf.mu.Lock()
if sf.conn != nil {
err = sf.conn.Close()
sf.conn = nil
}
sf.mu.Unlock()
return
}
func (sf *TCPClientProvider) setSerialConfig(serial.Config) {}
func (sf *TCPClientProvider) setTCPTimeout(t time.Duration) {
sf.timeout = t
}
// flush flushes pending data in the connection,
// returns io.EOF if connection is closed.
func (sf *TCPClientProvider) flush(b []byte) (err error) {
if err = sf.conn.SetReadDeadline(time.Now()); err != nil {
return
}
// timeout setting will be reset when reading
if _, err = sf.conn.Read(b); err != nil {
// Ignore timeout error
if netError, ok := err.(net.Error); ok && netError.Timeout() {
err = nil
}
}
return
}