woop/p2p/peer.go

package p2p

import (
	"bytes"
	"encoding/binary"
	"log"
	"net"
	"strings"
)

// Object for a p2p peer (node)
type Peer struct {
	// Ip address of the peer
	Ip string
	// Port number of the peer
	Port string
	// Public key of the peer
	PubKey string
}

// Send the message to the peer
func SendMessage(peer Peer, msg []byte) {
	// Construct normal p2p message
	payload := ConstructP2pMessage(byte(0), msg)

	send(peer.Ip, peer.Port, payload)
}

// Send the message to a list of peers
func BroadcastMessage(peers []Peer, msg []byte) {
	// Construct broadcast p2p message
	payload := ConstructP2pMessage(byte(17), msg)

	for _, peer := range peers {
		send(peer.Ip, peer.Port, payload)
	}
}

// Construct the p2p message as [messageType, payloadSize, payload]
func ConstructP2pMessage(msgType byte, payload []byte) []byte {

	firstByte := byte(17)        // messageType
	sizeBytes := make([]byte, 4) // payloadSize

	binary.BigEndian.PutUint32(sizeBytes, uint32(len(payload)))

	byteBuffer := bytes.NewBuffer([]byte{})
	byteBuffer.WriteByte(firstByte)
	byteBuffer.Write(sizeBytes)
	byteBuffer.Write(payload)
	return byteBuffer.Bytes()
}

// SocketClient is to connect a socket given a port and send the given message.
func sendWithSocketClient(ip, port string, message []byte) (res string) {
	log.Printf("Sending message to ip %s and port %s\n", ip, port)
	addr := strings.Join([]string{ip, port}, ":")
	conn, err := net.Dial("tcp", addr)

	if err != nil {
		log.Fatalln(err)
	}
	defer conn.Close()

	conn.Write(message)
	log.Printf("Sent to ip %s and port %s: %s\n", ip, port, message)

	// No ack (reply) message from the receiver for now.
	// TODO: think about
	return
}

// Send a message to another node with given port.
func send(ip, port string, message []byte) (returnMessage string) {
	returnMessage = sendWithSocketClient(ip, port, message)
	log.Println(returnMessage)
	return
}