first commit

internal/conn/conn.go

@@ -0,0 +1,85 @@
+package conn
+
+import (
+	"bytes"
+	"fmt"
+	"net"
+	"strings"
+	"time"
+
+	"github.com/onyx-and-iris/q3rcon/internal/packet"
+	log "github.com/sirupsen/logrus"
+)
+
+type UDPConn struct {
+	conn     *net.UDPConn
+	response packet.Response
+}
+
+func New(host string, port int) (UDPConn, error) {
+	udpAddr, err := net.ResolveUDPAddr("udp4", fmt.Sprintf("%s:%d", host, port))
+	if err != nil {
+		return UDPConn{}, err
+	}
+	conn, err := net.DialUDP("udp4", nil, udpAddr)
+	if err != nil {
+		return UDPConn{}, err
+	}
+	log.Infof("Outgoing address %s", conn.RemoteAddr())
+
+	return UDPConn{
+		conn:     conn,
+		response: packet.NewResponse(),
+	}, nil
+}
+
+func (c UDPConn) Write(buf []byte) (int, error) {
+	n, err := c.conn.Write(buf)
+	if err != nil {
+		return 0, err
+	}
+
+	return n, nil
+}
+
+func (c UDPConn) Listen(timeout time.Duration, resp chan<- string) {
+	c.conn.SetReadDeadline(time.Now().Add(timeout))
+	ch := make(chan struct{})
+	var sb strings.Builder
+	buf := make([]byte, 2048)
+
+	for {
+		select {
+		case <-ch:
+			resp <- sb.String()
+			return
+		default:
+			rlen, _, err := c.conn.ReadFromUDP(buf)
+			if err != nil {
+				e, ok := err.(net.Error)
+				if ok {
+					if e.Timeout() {
+						close(ch)
+					} else {
+						log.Error(e)
+					}
+				}
+			}
+			if rlen == 0 {
+				continue
+			}
+
+			if bytes.HasPrefix(buf, c.response.Header()) {
+				sb.Write(buf[len(c.response.Header()):rlen])
+			}
+		}
+	}
+}
+
+func (c UDPConn) Close() error {
+	err := c.conn.Close()
+	if err != nil {
+		return err
+	}
+	return nil
+}

internal/packet/request.go

@@ -0,0 +1,25 @@
+package packet
+
+import "fmt"
+
+type Request struct {
+	magic    []byte
+	password string
+}
+
+func NewRequest(password string) Request {
+	return Request{
+		magic:    []byte{'\xff', '\xff', '\xff', '\xff'},
+		password: password,
+	}
+}
+
+func (r Request) Header() []byte {
+	return append(r.magic, []byte("rcon")...)
+}
+
+func (r Request) Encode(cmd string) []byte {
+	datagram := r.Header()
+	datagram = append(datagram, fmt.Sprintf(" %s %s", r.password, cmd)...)
+	return datagram
+}

internal/packet/response.go

@@ -0,0 +1,13 @@
+package packet
+
+type Response struct {
+	magic []byte
+}
+
+func NewResponse() Response {
+	return Response{magic: []byte{'\xff', '\xff', '\xff', '\xff'}}
+}
+
+func (r Response) Header() []byte {
+	return append(r.magic, []byte("print\n")...)
+}