Initial commit

README.md

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+# udprelay
+
+Minimal example to show how to relay UDP packets.
+
+
+
+## Build
+
+```text
+go build -o udprelay main.go
+```
+
+
+## Usage
+```text
+./udprelay -addr "127.0.0.1:9998" -dest "192.168.1.10:9999"
+2022/02/21 15:41:50 Listening to 127.0.0.1:9998 - Relaying to 192.168.1.10:9999
+...
+2022/02/21 15:42:03 3 bytes relayed from 127.0.0.1:64078 to destination.
+```

go.mod

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+module git.t-juice.club/torjus/udprelay
+
+go 1.17

main.go

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+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"net"
+)
+
+func main() {
+	var addr, dest string
+	flag.StringVar(&addr, "addr", ":9999", "listen address")
+	flag.StringVar(&dest, "dest", "", "destination")
+
+	flag.Parse()
+
+	if dest == "" {
+		fmt.Println("Error: missing -dest")
+		fmt.Println("run with -h to see options.")
+
+		return
+	}
+
+	log.Printf("Listening to %s - Relaying to %s", addr, dest)
+	raddr, err := net.ResolveUDPAddr("udp", dest)
+	if err != nil {
+		panic(err)
+	}
+	udpConn, err := net.DialUDP("udp", nil, raddr)
+	if err != nil {
+		panic(err)
+	}
+	defer udpConn.Close()
+
+	laddr, err := net.ResolveUDPAddr("udp", addr)
+	if err != nil {
+		panic(err)
+	}
+
+	l, err := net.ListenUDP("udp", laddr)
+	if err != nil {
+		panic(err)
+	}
+	defer l.Close()
+
+	for {
+		buf := make([]byte, 1024)
+		n, raddr, err := l.ReadFrom(buf)
+		log.Printf("received packet %d\n", n)
+
+		if err != nil {
+			panic(err)
+		}
+
+		if _, err := udpConn.Write(buf[0:n]); err != nil {
+			log.Printf("error relaying data: %s\n", err)
+		}
+
+		log.Printf("%d bytes relayed from %s to destination.\n", n, raddr.String())
+	}
+}