sendhex.go

package main

import (
	"bufio"
	"bytes"
	"encoding/hex"
	"flag"
	"fmt"
	"io"
	"net"
	"os"
)

func main() {
	flag.Parse()

	// Read the hexdump from Stdin
	bs, err := readHexDump(os.Stdin)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	// "Dial" the destination
	conn, err := net.Dial("udp", flag.Arg(0))
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	defer conn.Close()

	// Send the packet
	if _, err := conn.Write(bs); err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
}

func readHexDump(r io.Reader) ([]byte, error) {
	space := []byte{' '}
	var hexBytes []byte
	sc := bufio.NewScanner(r)

	for sc.Scan() {
		line := sc.Bytes()
		firstSpace := bytes.Index(line, space)
		if firstSpace > 2 {
			// Line starts with something that is not a byte, it is probably
			// an offset. Strip it.
			line = line[firstSpace:]
		}
		hexBytes = append(hexBytes, bytes.Replace(line, space, nil, -1)...)
	}

	// Decode the hex data.

	dst := make([]byte, hex.DecodedLen(len(hexBytes)))
	if _, err := hex.Decode(dst, hexBytes); err != nil {
		return nil, err
	}

	return dst, nil
}