first init

udp_test.go

@@ -0,0 +1,166 @@
+package modbus
+
+import (
+	"net"
+	"os"
+	"testing"
+	"time"
+)
+
+func TestUDPSockWrapper(t *testing.T) {
+	var err     error
+	var usw     *udpSockWrapper
+	var sock1   *net.UDPConn
+	var sock2   *net.UDPConn
+	var addr    *net.UDPAddr
+	var txchan  chan []byte
+	var rxbuf   []byte
+	var count   int
+
+	addr, err = net.ResolveUDPAddr("udp", "localhost:5502")
+	if err != nil {
+		t.Errorf("failed to resolve udp address: %v", err)
+		return
+	}
+
+	txchan = make(chan []byte, 4)
+	// get a pair of UDP sockets ready to talk to each other
+	sock1, err = net.ListenUDP("udp", addr)
+	if err != nil {
+		t.Errorf("failed to listen on udp socket: %v", err)
+		return
+	}
+	err = sock1.SetReadDeadline(time.Now().Add(1 * time.Second))
+	if err != nil {
+		t.Errorf("failed to set deadline on udp socket: %v", err)
+		return
+	}
+
+	sock2, err = net.DialUDP("udp", nil, addr)
+	if err != nil {
+		t.Errorf("failed to open udp socket: %v", err)
+		return
+	}
+	// the feedTestPipe goroutine will forward any slice of bytes
+	// pushed into txchan over UDP to our test UDP sock wrapper object
+	go feedTestPipe(t, txchan, sock2)
+
+	usw = newUDPSockWrapper(sock1)
+	// push a valid RTU response (illegal data address) to the test pipe
+	txchan <- []byte{
+		0x31, 0x82, // unit id and response code
+		0x02,       // exception code
+		0xc1, 0x6e, // CRC
+	}
+	// then push random junk
+	txchan <-[]byte{
+		0xaa, 0xbb, 0xcc,
+	}
+	// then some more
+	txchan <-[]byte{
+		0xdd, 0xee,
+	}
+
+	// attempt to read 3 bytes: we should get them as the first datagram
+	// is 5 bytes long
+	rxbuf = make([]byte, 3)
+	count, err = usw.Read(rxbuf)
+	if err != nil {
+		t.Errorf("usw.Read() should have succeeded, got: %v", err)
+	}
+	if count != 3 {
+		t.Errorf("expected 3 bytes, got: %v", count)
+	}
+	for idx, val := range []byte{
+		0x31, 0x82, 0x02,
+	} {
+		if rxbuf[idx] != val {
+			t.Errorf("expected 0x%02x at pos %v, got: 0x%02x",
+				val, idx, rxbuf[idx])
+		}
+	}
+
+	// attempt to read 1 byte: we should get the 4th byte of the
+	// first datagram, of which we've been holding on to bytes #4 and 5
+	rxbuf = make([]byte, 1)
+	count, err = usw.Read(rxbuf)
+	if err != nil {
+		t.Errorf("usw.Read() should have succeeded, got: %v", err)
+	}
+	if count != 1 {
+		t.Errorf("expected 1 byte, got: %v", count)
+	}
+	if rxbuf[0] != 0xc1 {
+		t.Errorf("expected 0xc1 at pos 0, got: 0x%02x", rxbuf[0])
+	}
+
+	// attempt to read 5 bytes: we should get the last byte of the
+	// first datagram, which the udpSockWrapper object still holds in
+	// its buffer
+	rxbuf = make([]byte, 5)
+	count, err = usw.Read(rxbuf)
+	if err != nil {
+		t.Errorf("usw.Read() should have succeeded, got: %v", err)
+	}
+	if count != 1 {
+		t.Errorf("expected 1 byte, got: %v", count)
+	}
+	if rxbuf[0] != 0x6e {
+		t.Errorf("expected 0x6e at pos 0, got: 0x%02x", rxbuf[0])
+	}
+
+	// attempt to read 10 bytes: we should get all 3 bytes of the 2nd
+	// datagram
+	rxbuf = make([]byte, 10)
+	count, err = usw.Read(rxbuf)
+	if err != nil {
+		t.Errorf("usw.Read() should have succeeded, got: %v", err)
+	}
+	if count != 3 {
+		t.Errorf("expected 3 bytes, got: %v", count)
+	}
+	for idx, val := range []byte{
+		0xaa, 0xbb, 0xcc,
+	} {
+		if rxbuf[idx] != val {
+			t.Errorf("expected 0x%02x at pos %v, got: 0x%02x",
+				val, idx, rxbuf[idx])
+		}
+	}
+
+	// attempt to read 40 bytes: we should get both bytes of the 3rd
+	// datagram
+	rxbuf = make([]byte, 40)
+	count, err = usw.Read(rxbuf)
+	if err != nil {
+		t.Errorf("usw.Read() should have succeeded, got: %v", err)
+	}
+	if count != 2 {
+		t.Errorf("expected 2 bytes, got: %v", count)
+	}
+	for idx, val := range []byte{
+		0xdd, 0xee,
+	} {
+		if rxbuf[idx] != val {
+			t.Errorf("expected 0x%02x at pos %v, got: 0x%02x",
+				val, idx, rxbuf[idx])
+		}
+	}
+
+	// attempt to read 7 bytes: we should get a read timeout as we've
+	// consumed all bytes from all datagrams and no more are coming
+	rxbuf = make([]byte, 7)
+	count, err = usw.Read(rxbuf)
+	if !os.IsTimeout(err) {
+		t.Errorf("usw.Read() should have failed with a timeout error, got: %v", err)
+	}
+	if count != 0 {
+		t.Errorf("expected 0 bytes, got: %v", count)
+	}
+
+	// cleanup
+	sock1.Close()
+	sock2.Close()
+
+	return
+}