Implement 'startnode' CLI command

cli.go

@@ -19,6 +19,7 @@ func (cli *CLI) printUsage() {
 	fmt.Println("  printchain - Print all the blocks of the blockchain")
 	fmt.Println("  reindexutxo - Rebuilds the UTXO set")
 	fmt.Println("  send -from FROM -to TO -amount AMOUNT - Send AMOUNT of coins from FROM address to TO")
+	fmt.Println("  startnode -node-id NODE_ID - Start a node with specified ID")
 }
 
 func (cli *CLI) validateArgs() {
@@ -39,12 +40,14 @@ func (cli *CLI) Run() {
 	printChainCmd := flag.NewFlagSet("printchain", flag.ExitOnError)
 	reindexUTXOCmd := flag.NewFlagSet("reindexutxo", flag.ExitOnError)
 	sendCmd := flag.NewFlagSet("send", flag.ExitOnError)
+	startNodeCmd := flag.NewFlagSet("startnode", flag.ExitOnError)
 
 	getBalanceAddress := getBalanceCmd.String("address", "", "The address to get balance for")
 	createBlockchainAddress := createBlockchainCmd.String("address", "", "The address to send genesis block reward to")
 	sendFrom := sendCmd.String("from", "", "Source wallet address")
 	sendTo := sendCmd.String("to", "", "Destination wallet address")
 	sendAmount := sendCmd.Int("amount", 0, "Amount to send")
+	startNodeID := startNodeCmd.Int("node-id", 0, "Node ID")
 
 	switch os.Args[1] {
 	case "getbalance":
@@ -72,13 +75,18 @@ func (cli *CLI) Run() {
 		if err != nil {
 			log.Panic(err)
 		}
+	case "reindexutxo":
+		err := reindexUTXOCmd.Parse(os.Args[2:])
+		if err != nil {
+			log.Panic(err)
+		}
 	case "send":
 		err := sendCmd.Parse(os.Args[2:])
 		if err != nil {
 			log.Panic(err)
 		}
-	case "reindexutxo":
-		err := reindexUTXOCmd.Parse(os.Args[2:])
+	case "startnode":
+		err := startNodeCmd.Parse(os.Args[2:])
 		if err != nil {
 			log.Panic(err)
 		}
@@ -127,4 +135,12 @@ func (cli *CLI) Run() {
 
 		cli.send(*sendFrom, *sendTo, *sendAmount)
 	}
+
+	if startNodeCmd.Parsed() {
+		if *startNodeID == 0 {
+			startNodeCmd.Usage()
+			os.Exit(1)
+		}
+		cli.startNode(*startNodeID)
+	}
 }

cli_startnode.go

@@ -0,0 +1,8 @@
+package main
+
+import "fmt"
+
+func (cli *CLI) startNode(nodeID int) {
+	fmt.Printf("Starting node %d\n", nodeID)
+	StartServer(nodeID)
+}

server.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net"
+)
+
+func handleConnection(conn net.Conn) {
+	io.Copy(conn, conn)
+	conn.Close()
+}
+
+// StartServer starts a node
+func StartServer(nodeID int) {
+	ln, err := net.Listen("tcp", fmt.Sprintf(":%d", nodeID))
+	if err != nil {
+		log.Panic(err)
+	}
+	defer ln.Close()
+
+	for {
+		conn, err := ln.Accept()
+		if err != nil {
+			log.Panic(err)
+		}
+		go handleConnection(conn)
+	}
+}