tcp_transport_test.go

package modbus

import (
	"io"
	"net"
	"testing"
	"time"
)

func TestAssembleMBAPFrame(t *testing.T) {
	var tt *tcpTransport
	var frame []byte

	tt = &tcpTransport{}

	frame = tt.assembleMBAPFrame(0x9219, &pdu{
		unitId:       0x33,
		functionCode: 0x11,
		payload:      []byte{0x22, 0x33, 0x44, 0x55},
	})
	// expect 7 bytes of MBAP header + 1 bytes of function code + 4 bytes of payload
	if len(frame) != 12 {
		t.Errorf("expected 12 bytes, got %v", len(frame))
	}
	for i, b := range []byte{
		0x92, 0x19, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x00, 0x06, // length (big endian)
		0x33, 0x11, // unit id and function code
		0x22, 0x33, // payload
		0x44, 0x55, // payload
	} {
		if frame[i] != b {
			t.Errorf("expected 0x%02x at position %v, got 0x%02x", b, i, frame[i])
		}
	}

	frame = tt.assembleMBAPFrame(0x921a, &pdu{
		unitId:       0x31,
		functionCode: 0x06,
		payload:      []byte{0x12, 0x34},
	})
	// expect 7 bytes of MBAP header + 1 bytes of function code + 2 bytes of payload
	if len(frame) != 10 {
		t.Errorf("expected 10 bytes, got %v", len(frame))
	}
	for i, b := range []byte{
		0x92, 0x1a, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x00, 0x04, // length (big endian)
		0x31, 0x06, // unit id and function code
		0x12, 0x34, // payload
	} {
		if frame[i] != b {
			t.Errorf("expected 0x%02x at position %v, got 0x%02x", b, i, frame[i])
		}
	}

}

func TestTCPTransportReadResponse(t *testing.T) {
	var tt *tcpTransport
	var p1, p2 net.Conn
	var txchan chan []byte
	var err error
	var res *pdu

	txchan = make(chan []byte, 2)
	p1, p2 = net.Pipe()
	go feedTestPipe(t, txchan, p1)

	tt = newTCPTransport(p2, 10*time.Millisecond, nil)
	tt.lastTxnId = 0x9218

	// read a valid response
	txchan <- []byte{
		0x92, 0x18, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x00, 0x04, // length (big endian)
		0x31, 0x06, // unit id and function code
		0x12, 0x34, // payload
	}
	res, err = tt.readResponse()
	if err != nil {
		t.Errorf("readResponse() should have succeeded, got %v", err)
	}
	if res.unitId != 0x31 {
		t.Errorf("expected 0x31 as unit id, got 0x%02x", res.unitId)
	}
	if res.functionCode != 0x06 {
		t.Errorf("expected 0x06 as function code, got 0x%02x", res.functionCode)
	}
	if len(res.payload) != 2 {
		t.Errorf("expected a length of 2, got %v", len(res.payload))
	}
	if res.payload[0] != 0x12 || res.payload[1] != 0x34 {
		t.Errorf("expected {0x12, 0x34} as payload, got {0x%02x, 0x%02x}",
			res.payload[0], res.payload[1])
	}

	// read a frame with an unexpected transaction id followed by a frame with a
	// matching transaction id: the first frame should be silently skipped
	txchan <- []byte{
		0x92, 0x19, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x00, 0x04, // length (big endian)
		0x31, 0x06, // unit id and function code
		0x12, 0x34, // payload
	}
	txchan <- []byte{
		0x92, 0x18, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x00, 0x04, // length (big endian)
		0x39, 0x02, // unit id and function code
		0x10, 0x01, // payload
	}
	res, err = tt.readResponse()
	if err != nil {
		t.Errorf("readResponse() should have succeeded, got %v", err)
	}
	if res.unitId != 0x39 {
		t.Errorf("expected 0x39 as unit id, got 0x%02x", res.unitId)
	}
	if res.functionCode != 0x02 {
		t.Errorf("expected 0x02 as function code, got 0x%02x", res.functionCode)
	}
	if len(res.payload) != 2 {
		t.Errorf("expected a length of 2, got %v", len(res.payload))
	}
	if res.payload[0] != 0x10 || res.payload[1] != 0x01 {
		t.Errorf("expected {0x10, 0x01 as payload, got {0x%02x, 0x%02x}",
			res.payload[0], res.payload[1])
	}

	// read a frame with an illegal length, preceded by a frame with an unexpected
	// protocol ID. While the first frame should be skipped without error,
	// the second should yield an ErrProtocolError.
	txchan <- []byte{
		0x92, 0x18, // transaction identifier (big endian)
		0x00, 0x01, // protocol identifier
		0x00, 0x04, // length (big endian)
		0x31, 0x06, // unit id and function code
		0x12, 0x34, // payload
	}
	txchan <- []byte{
		0x92, 0x18, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x00, 0x01, // length (big endian)
		0x31, // unit id
	}
	_, err = tt.readResponse()
	if err != ErrProtocolError {
		t.Errorf("readResponse() should have returned ErrProtocolError, got %v", err)
	}

	// read a valid frame again
	txchan <- []byte{
		0x92, 0x18, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x00, 0x0a, // length (big endian)
		0x31, 0x32, // unit id and function code
		0x44, 0x55, // payload
		0x66, 0x77, // payload
		0x88, 0x99, // payload
		0xaa, 0xbb, // payload
	}
	res, err = tt.readResponse()
	if err != nil {
		t.Errorf("readResponse() should have succeeded, got %v", err)
	}
	if res.unitId != 0x31 {
		t.Errorf("expected 0x31 as unit id, got 0x%02x", res.unitId)
	}
	if res.functionCode != 0x32 {
		t.Errorf("expected 0x32 as response code, got 0x%02x", res.functionCode)
	}
	if len(res.payload) != 8 {
		t.Errorf("expected a length of 8, got %v", len(res.payload))
	}
	for i, b := range []byte{
		0x44, 0x55,
		0x66, 0x77,
		0x88, 0x99,
		0xaa, 0xbb,
	} {
		if res.payload[i] != b {
			t.Errorf("expected 0x%02x at position %v, got 0x%02x",
				b, i, res.payload[i])
		}
	}

	// read a huge frame
	txchan <- []byte{
		0x92, 0x18, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x10, 0x0a, // length (big endian)
		0x31, // unit id
	}
	_, err = tt.readResponse()
	if err != ErrProtocolError {
		t.Errorf("readResponse() should have returned ErrProtocolError, got %v", err)
	}

	p1.Close()
	p2.Close()

}

func TestTCPTransportReadRequest(t *testing.T) {
	var tt *tcpTransport
	var p1, p2 net.Conn
	var txchan chan []byte
	var err error
	var req *pdu

	txchan = make(chan []byte, 2)
	p1, p2 = net.Pipe()
	go feedTestPipe(t, txchan, p1)

	tt = newTCPTransport(p2, 10*time.Millisecond, nil)
	tt.lastTxnId = 0x0a00

	// push three frames in a row:
	//  - the first with an unknown protocol ID
	txchan <- []byte{
		0x92, 0x18, // transaction identifier (big endian)
		0x00, 0x01, // protocol identifier
		0x00, 0x04, // length (big endian)
		0x31, 0x06, // unit id and function code
		0x12, 0x34, // payload
	}
	//  - the second with an illegal length
	txchan <- []byte{
		0x92, 0x18, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x00, 0x01, // length (big endian)
		0x31, // unit id
	}
	// - the thid with a valid request
	txchan <- []byte{
		0x92, 0x18, // transaction identifier (big endian)
		0x00, 0x00, // protocol identifier
		0x00, 0x0a, // length (big endian)
		0xfa, 0x04, // unit id and function code
		0x44, 0x55, // payload
		0x66, 0x77, // payload
		0x88, 0x99, // payload
		0xaa, 0xbb, // payload
	}

	// read the first frame
	req, err = tt.ReadRequest()
	if req != nil || err != ErrUnknownProtocolId {
		t.Errorf("ReadRequest() should have returned {nil, ErrUnknownProtocolId}, got {%v, %v}", req, err)
	}
	if tt.lastTxnId != 0x0a00 {
		t.Errorf("tt.lastTxnId should have been 0x0a00, saw 0x%02x", tt.lastTxnId)
	}

	// read the second frame
	req, err = tt.ReadRequest()
	if req != nil || err != ErrProtocolError {
		t.Errorf("ReadRequest() should have returned {nil, ErrProtocolError}, got {%v, %v}", req, err)
	}
	if tt.lastTxnId != 0x0a00 {
		t.Errorf("tt.lastTxnId should have been 0x0a00, saw 0x%02x", tt.lastTxnId)
	}

	// read the third frame
	req, err = tt.ReadRequest()
	if err != nil {
		t.Errorf("ReadRequest() should have succeeded, got %v", err)
	}
	if req == nil {
		t.Errorf("ReadREsponse() should have returned a non-nil request")
	}
	if req.unitId != 0xfa {
		t.Errorf("expected 0xfa as unit id, got 0x%02x", req.unitId)
	}
	if req.functionCode != 0x04 {
		t.Errorf("expected 0x04 as response code, got 0x%02x", req.functionCode)
	}
	if len(req.payload) != 8 {
		t.Errorf("expected a length of 8, got %v", len(req.payload))
	}
	for i, b := range []byte{
		0x44, 0x55,
		0x66, 0x77,
		0x88, 0x99,
		0xaa, 0xbb,
	} {
		if req.payload[i] != b {
			t.Errorf("expected 0x%02x at position %v, got 0x%02x",
				b, i, req.payload[i])
		}
	}
	if tt.lastTxnId != 0x9218 {
		t.Errorf("tt.lastTxnId should have been 0x0a00, saw 0x%02x", tt.lastTxnId)
	}

	return
}

func TestTCPTransportWriteResponse(t *testing.T) {
	var tt *tcpTransport
	var p1, p2 net.Conn
	var done chan bool
	var err error

	done = make(chan bool, 0)
	p1, p2 = net.Pipe()
	go func(t *testing.T, pipe net.Conn, done chan bool) {
		var err error
		var rxbuf []byte
		var expected []byte

		expected = []byte{
			0xc0, 0x1f, // transaction identifier (big endian)
			0x00, 0x00, // protocol identifier
			0x00, 0x0b, // length (big endian)
			0x17, 0x06, // unit id and function code
			0x44, 0x55, // payload
			0x66, 0x77, // payload
			0x88, 0x99, // payload
			0xaa, 0xbb, // payload
			0xf4, // payload
		}

		rxbuf = make([]byte, len(expected))
		_, err = io.ReadFull(pipe, rxbuf)
		if err != nil {
			t.Errorf("failed to read frame: %v", err)
		}

		for i, b := range expected {
			if rxbuf[i] != b {
				t.Errorf("expected 0x%02x at position %v, got 0x%02x",
					b, i, rxbuf[i])
			}
		}

		done <- true
		return
	}(t, p2, done)

	tt = newTCPTransport(p1, 10*time.Millisecond, nil)
	tt.lastTxnId = 0xc01f

	err = tt.WriteResponse(&pdu{
		unitId:       0x17,
		functionCode: 0x06,
		payload: []byte{
			0x44, 0x55, // payload
			0x66, 0x77, // payload
			0x88, 0x99, // payload
			0xaa, 0xbb, // payload
			0xf4, // payload
		},
	})
	if err != nil {
		t.Errorf("WriteResponse() should have succeeded, got %v", err)
	}

	// wait for the checker goroutine to return
	<-done

	return
}