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main.go
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main.go
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package main
import (
"bufio"
"encoding/json"
"fmt"
"log"
"net"
"os"
"errors"
"github.com/kisom/aescrypt/secretbox"
)
const (
UpAndMulticast = (net.FlagUp | net.FlagMulticast)
Secret = "$1HLK#5qAFlEH$4TM5W*TSM18&dW5zFh8f7TujH7#RobIgIn"
)
var BrotocolGroup *net.UDPAddr = &net.UDPAddr{IP: []byte{225,0,0,1}, Port: 12345}
type Message struct {
Sender, Body string
}
type Listener interface {
Incoming() <-chan Message
}
type Sender interface {
Send(msg Message)
}
type room struct {
incoming chan Message
outgoing chan Message
}
func (r *room) Incoming() <-chan Message {
return r.incoming
}
func (r *room) Send(msg Message) {
r.outgoing <- msg
}
func NewRoom() (r *room) {
return &room{
incoming: make(chan Message),
outgoing: make(chan Message),
}
}
func getMcastInterface() (ifi *net.Interface, err error) {
ifis, err := net.Interfaces()
if err != nil {
return
}
for _, ifi := range ifis {
if (ifi.Flags & UpAndMulticast) == UpAndMulticast && (ifi.Flags & net.FlagLoopback) != net.FlagLoopback{
return &ifi, nil
}
}
return &net.Interface{}, errors.New("Could not find interface that was up and supports multicast")
}
func main() {
fmt.Print("Who are you? ")
var user string
fmt.Scanln(&user)
r := NewRoom()
userInput := make(chan string)
go r.listenLoop()
go inputListener(userInput)
go r.sendLoop(user)
for {
select {
case msg := <-r.Incoming():
if msg.Sender == user {
continue
}
log.Printf("%s: %s", msg.Sender, msg.Body)
case body := <-userInput:
r.Send(Message{Sender: user, Body: body})
}
}
}
func inputListener(userInput chan string) {
rdr := bufio.NewReader(os.Stdin)
for {
line, err := rdr.ReadString('\n')
if err != nil {
log.Fatal("Error reading your input", err)
}
userInput <- line
}
}
func (r *room) sendLoop(user string) {
conn, err := net.ListenUDP("udp4", BrotocolGroup)
if err != nil {
log.Fatal("Error listening UDP: ", err)
}
defer conn.Close()
for {
msg := <-r.outgoing
b, err := json.Marshal(msg)
if err != nil {
log.Fatal("Error encoding: ", err)
}
box, ok := secretbox.Seal(b, []byte(Secret))
if !ok {
log.Println("Couldn't encrypt message. It wasn't sent.")
continue
}
_, err = conn.WriteToUDP(box, BrotocolGroup)
if err != nil {
log.Printf("Error sending data: %s", err)
}
}
}
func (r *room) listenLoop() {
ifi, err := getMcastInterface()
log.Printf("Using interface: %v\n", ifi)
if err != nil {
log.Fatal("Error obtaining multicast interface: ", err)
}
conn, err := net.ListenMulticastUDP("udp4", ifi, BrotocolGroup)
if err != nil {
log.Fatal(err)
}
defer conn.Close()
for {
payload := make([]byte, 4096)
n, _, err := conn.ReadFromUDP(payload)
if err != nil {
log.Println("Error reading message: ", err)
}
var msg Message
jsonMsg, ok := secretbox.Open(payload[:n], []byte(Secret))
if !ok {
log.Println("Couldn't decrypt message")
continue
}
json.Unmarshal(jsonMsg, &msg)
r.incoming <- msg
}
}