Implement 'version' command

server.go

@@ -1,25 +1,109 @@
 package main
 
 import (
+	"bytes"
+	"encoding/gob"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"log"
 	"net"
 )
 
+const protocol = "tcp"
+const dnsNodeID = 3000
+const nodeVersion = 1
+const commandLength = 12
+
+var nodeAddress string
+
+type verzion struct {
+	Version  int
+	AddrFrom string
+}
+
+func commandToBytes(command string) []byte {
+	var bytes [commandLength]byte
+
+	for i, c := range command {
+		bytes[i] = byte(c)
+	}
+
+	return bytes[:]
+}
+
+func bytesToCommand(bytes []byte) string {
+	var command []byte
+
+	for _, b := range bytes {
+		if b != 0x0 {
+			command = append(command, b)
+		}
+	}
+
+	return fmt.Sprintf("%s", command)
+}
+
+func extractCommand(request []byte) []byte {
+	return request[:commandLength]
+}
+
+func sendVersion(addr string) {
+	var payload bytes.Buffer
+
+	enc := gob.NewEncoder(&payload)
+	err := enc.Encode(verzion{nodeVersion, nodeAddress})
+	if err != nil {
+		log.Panic(err)
+	}
+
+	request := append(commandToBytes("version"), payload.Bytes()...)
+
+	conn, err := net.Dial(protocol, addr)
+	if err != nil {
+		log.Panic(err)
+	}
+	defer conn.Close()
+
+	fmt.Printf("%x\n", request)
+	_, err = io.Copy(conn, bytes.NewReader(request))
+	if err != nil {
+		log.Panic(err)
+	}
+}
+
 func handleConnection(conn net.Conn) {
-	io.Copy(conn, conn)
+	request, err := ioutil.ReadAll(conn)
+	if err != nil {
+		log.Panic(err)
+	}
+	command := bytesToCommand(request[:commandLength])
+
+	switch command {
+	case "version":
+		fmt.Printf("Received %s command", command)
+		// send verack
+		// send addr
+	default:
+		fmt.Println("Unknown command received!")
+	}
+
 	conn.Close()
 }
 
 // StartServer starts a node
 func StartServer(nodeID int) {
-	ln, err := net.Listen("tcp", fmt.Sprintf(":%d", nodeID))
+	nodeAddress = fmt.Sprintf("localhost:%d", nodeID)
+	ln, err := net.Listen(protocol, nodeAddress)
 	if err != nil {
 		log.Panic(err)
 	}
 	defer ln.Close()
 
+	if nodeID != dnsNodeID {
+		sendVersion(fmt.Sprintf("localhost:%d", dnsNodeID))
+	}
+
 	for {
 		conn, err := ln.Accept()
 		if err != nil {