diff --git a/main.go b/main.go
index d9afd47..9af3cdf 100644
--- a/main.go
+++ b/main.go
@@ -6,12 +6,20 @@ import (
 	"encoding/binary"
 	"fmt"
 	"net"
+	"os"
+	"os/signal"
+	"syscall"
 	"time"
 
 	"github.com/nonoo/kappanhang/log"
 )
 
 var conn *net.UDPConn
+var localSID uint32
+var remoteSID uint32
+var sendSeq uint16
+var longPingSendSeq uint16
+var authID [6]byte
 
 func send(d []byte) {
 	_, err := conn.Write(d)
@@ -36,9 +44,27 @@ func read() ([]byte, error) {
 	return b[:n], err
 }
 
+func setupCloseHandler() {
+	c := make(chan os.Signal)
+	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
+	go func() {
+		<-c
+		log.Print("disconnecting")
+		send([]byte{0x40, 0x00, 0x00, 0x00, 0x00, 0x00, byte(sendSeq), byte(sendSeq >> 8), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
+			0x00, 0x00, 0x00, 0x30, 0x01, 0x01, 0x00, byte(longPingSendSeq),
+			byte(longPingSendSeq >> 8), 0x00, authID[0], authID[1], authID[2], authID[3], authID[4], authID[5],
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00})
+		os.Exit(0)
+	}()
+}
+
 func main() {
 	log.Init()
 	parseArgs()
+	setupCloseHandler()
 
 	hostPort := fmt.Sprint(connectAddress, ":", connectPort)
 	log.Print("connecting to ", hostPort)
@@ -53,7 +79,7 @@ func main() {
 
 	// Constructing the local session ID by combining the local IP address and port.
 	laddr := conn.LocalAddr().(*net.UDPAddr)
-	localSID := binary.BigEndian.Uint32(laddr.IP[len(laddr.IP)-4:])<<16 | uint32(laddr.Port&0xffff)
+	localSID = binary.BigEndian.Uint32(laddr.IP[len(laddr.IP)-4:])<<16 | uint32(laddr.Port&0xffff)
 	log.Debugf("using session id %.8x", localSID)
 
 	send([]byte{0x10, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), 0x00, 0x00, 0x00, 0x00})
@@ -62,7 +88,6 @@ func main() {
 	// send([]byte{0x15, 0x00, 0x00, 0x00, 0x07, 0x00, 0x02, 0x00, byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), 0x00, 0x00, 0x00, 0x00, 0x00, 0x70, 0x3e, 0x10, 0x00})
 	// send([]byte{0x10, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), 0x00, 0x00, 0x00, 0x00})
 
-	var remoteSID uint32
 	for {
 		r, _ := read()
 		if bytes.Equal(r[:8], []byte{0x10, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00}) {
@@ -75,8 +100,8 @@ func main() {
 
 	send([]byte{0x10, 0x00, 0x00, 0x00, 0x06, 0x00, 0x01, 0x00, byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID)})
 	send([]byte{0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID),
-		0x00, 0x00, 0x00, 0x70, 0x01, 0x00, 0x00, 0x22,
-		0x00, 0x00, 0x09, 0x27, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x70, 0x01, 0x00, 0x00, byte(longPingSendSeq),
+		byte(longPingSendSeq >> 8), 0x00, 0x09, 0x27, 0x00, 0x00, 0x00, 0x00,
 		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
@@ -90,14 +115,12 @@ func main() {
 		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00})
 
-	var sendSeq uint8
-	var lastReceivedSeq uint8
+	var lastReceivedSeq uint16
 	var receivedSeq bool
 	var lastPingAt time.Time
 	var lastLongPingAt time.Time
 	var errCount int
 	var randID [4]byte
-	var authID [6]byte
 	for {
 		r, err := read()
 		if err != nil {
@@ -130,25 +153,25 @@ func main() {
 			}
 		}
 		if len(r) == 21 && bytes.Equal(r[1:6], []byte{0x00, 0x00, 0x00, 0x07, 0x00}) {
-			gotSeq := r[6]
+			// Replying to the radio.
+			// Example request from radio: 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x1c, 0x0e, 0xe4, 0x35, 0xdd, 0x72, 0xbe, 0xd9, 0xf2, 0x63, 0x00, 0x57, 0x2b, 0x12, 0x00
+			// Example answer from PC:     0x15, 0x00, 0x00, 0x00, 0x07, 0x00, 0x1c, 0x0e, 0xbe, 0xd9, 0xf2, 0x63, 0xe4, 0x35, 0xdd, 0x72, 0x01, 0x57, 0x2b, 0x12, 0x00
+			gotSeq := binary.LittleEndian.Uint16(r[6:8])
 			if receivedSeq && lastReceivedSeq+1 != gotSeq {
 				log.Error("packet loss detected")
 			}
 			lastReceivedSeq = gotSeq
 			receivedSeq = true
 
-			// Replying to the radio.
-			// Example request from radio: 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x1c, 0x0e, 0xe4, 0x35, 0xdd, 0x72, 0xbe, 0xd9, 0xf2, 0x63, 0x00, 0x57, 0x2b, 0x12, 0x00
-			// Example answer from PC:     0x15, 0x00, 0x00, 0x00, 0x07, 0x00, 0x1c, 0x0e, 0xbe, 0xd9, 0xf2, 0x63, 0xe4, 0x35, 0xdd, 0x72, 0x01, 0x57, 0x2b, 0x12, 0x00
-			send([]byte{0x15, 0x00, 0x00, 0x00, 0x07, 0x00, gotSeq, r[7], byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), 0x01,
+			send([]byte{0x15, 0x00, 0x00, 0x00, 0x07, 0x00, byte(gotSeq), byte(gotSeq >> 8), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), 0x01,
 				r[17], r[18], r[19], r[20]})
 		}
 		if len(r) == 16 && bytes.Equal(r[:6], []byte{0x10, 0x00, 0x00, 0x00, 0x00, 0x00}) {
 			// Replying to the radio.
 			// Example request from radio: 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x13, 0x00, 0xe4, 0x35, 0xdd, 0x72, 0xbe, 0xd9, 0xf2, 0x63
 			// Example answer from PC:     0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x13, 0x00, 0xbe, 0xd9, 0xf2, 0x63, 0xe4, 0x35, 0xdd, 0x72
-			gotSeq := r[6]
-			send([]byte{0x10, 0x00, 0x00, 0x00, 0x00, 0x00, gotSeq, r[7], byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID)})
+			gotSeq := binary.LittleEndian.Uint16(r[6:8])
+			send([]byte{0x10, 0x00, 0x00, 0x00, 0x00, 0x00, byte(gotSeq), byte(gotSeq >> 8), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID)})
 		}
 
 		if time.Since(lastPingAt) >= 100*time.Millisecond {
@@ -158,13 +181,13 @@ func main() {
 			if err != nil {
 				log.Fatal(err)
 			}
-			send([]byte{0x15, 0x00, 0x00, 0x00, 0x07, 0x00, sendSeq, 0x00, byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), 0x01,
+			send([]byte{0x15, 0x00, 0x00, 0x00, 0x07, 0x00, byte(sendSeq), byte(sendSeq >> 8), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), 0x01,
 				randID[0], randID[1], randID[2], randID[3]})
-			send([]byte{0x10, 0x00, 0x00, 0x00, 0x03, 0x00, sendSeq, 0x00, byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID)})
+			send([]byte{0x10, 0x00, 0x00, 0x00, 0x03, 0x00, byte(sendSeq), byte(sendSeq >> 8), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID)})
 			sendSeq++
 			lastPingAt = time.Now()
 
-			if time.Since(lastLongPingAt) >= 60*time.Second {
+			if time.Since(lastLongPingAt) >= 30*time.Second {
 				// Example request from PC:  0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0d, 0x00,
 				//                           0xbb, 0x41, 0x3f, 0x2b, 0xe6, 0xb2, 0x7b, 0x7b,
 				//                           0x00, 0x00, 0x00, 0x30, 0x01, 0x05, 0x00, 0x02,
@@ -181,9 +204,9 @@ func main() {
 				//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 				//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 				//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
-				send([]byte{0x40, 0x00, 0x00, 0x00, 0x00, 0x00, sendSeq, 0x00, byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
-					0x00, 0x00, 0x00, 0x30, 0x01, 0x05, 0x00, 0x3f,
-					0x00, 0x00, authID[0], authID[1], authID[2], authID[3], authID[4], authID[5],
+				send([]byte{0x40, 0x00, 0x00, 0x00, 0x00, 0x00, byte(sendSeq), byte(sendSeq >> 8), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
+					0x00, 0x00, 0x00, 0x30, 0x01, 0x05, 0x00, byte(longPingSendSeq),
+					byte(longPingSendSeq >> 8), 0x00, authID[0], authID[1], authID[2], authID[3], authID[4], authID[5],
 					0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 					0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 					0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,