Merge branch 'master' of https://github.com/mycoralhealth/blockchain-…

…tutorial

p2p/README.md

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+# Peer 2 Peer Blockchain Tutorial
+
+### Getting started
+
+In your 1st terminal `go run -race main.go -secio -l 10000`
+
+Follow the instructions in your 1st terminal and copy and paste the given command into your 2nd terminal e.g. `go run main.go -l 10001 -d /ip4/127.0.0.1/tcp/10000/ipfs/QmZ8NayvdXc2U2A1cwh9qGaHK7uxXXVrZQEYwDqbfFydfj -secio`
+
+Follow the instructions in your 2nd terminal and copy and paste the given command into your 3rd terminal e.g. `go run main.go -l 10002 -d /ip4/127.0.0.1/tcp/10001/ipfs/QmRAj9JJVKRJmWHbDKzvzKDVVFPWxuWYio3bPym4SgGPgF -secio`
+
+Type a BPM into any of your terminals and watch your blockchain be broadcast to all terminals!
+
+

p2p/main.go

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+package main
+
+import (
+	"bufio"
+	"context"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	mrand "math/rand"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	gologging "gx/ipfs/QmQvJiADDe7JR4m968MwXobTCCzUqQkP87aRHe29MEBGHV/go-logging"
+	net "gx/ipfs/QmRQX1yaPQFynWkByKcQTPpy3uC21oXZ5X32KEcLZnefz8/go-libp2p-net"
+	golog "gx/ipfs/QmRb5jh8z2E8hMGN2tkvs1yHynUanqnZ3UeKwgN1i9P1F8/go-log"
+	host "gx/ipfs/QmWPKovoJxF2bfiYLQK6xPeFvMJW8hX6RFRuA9bv6cURha/go-libp2p-host"
+	ma "gx/ipfs/QmWWQ2Txc2c6tqjsBpzg5Ar652cHPGNsQQp2SejkNmkUMb/go-multiaddr"
+	pstore "gx/ipfs/QmXauCuJzmzapetmC6W4TuDJLL1yFFrVzSHoWv8YdbmnxH/go-libp2p-peerstore"
+	peer "gx/ipfs/QmZoWKhxUmZ2seW4BzX6fJkNR8hh9PsGModr7q171yq2SS/go-libp2p-peer"
+	crypto "gx/ipfs/QmaPbCnUMBohSGo3KnxEa2bHqyJVVeEEcwtqJAYxerieBo/go-libp2p-crypto"
+
+	"github.com/davecgh/go-spew/spew"
+	libp2p "github.com/libp2p/go-libp2p"
+)
+
+// Block represents each 'item' in the blockchain
+type Block struct {
+	Index     int
+	Timestamp string
+	BPM       int
+	Hash      string
+	PrevHash  string
+}
+
+// Blockchain is a series of validated Blocks
+var Blockchain []Block
+
+var mutex = &sync.Mutex{}
+
+// makeBasicHost creates a LibP2P host with a random peer ID listening on the
+// given multiaddress. It will use secio if secio is true.
+func makeBasicHost(listenPort int, secio bool, randseed int64) (host.Host, error) {
+
+	// If the seed is zero, use real cryptographic randomness. Otherwise, use a
+	// deterministic randomness source to make generated keys stay the same
+	// across multiple runs
+	var r io.Reader
+	if randseed == 0 {
+		r = rand.Reader
+	} else {
+		r = mrand.New(mrand.NewSource(randseed))
+	}
+
+	// Generate a key pair for this host. We will use it
+	// to obtain a valid host ID.
+	priv, _, err := crypto.GenerateKeyPairWithReader(crypto.RSA, 2048, r)
+	if err != nil {
+		return nil, err
+	}
+
+	opts := []libp2p.Option{
+		libp2p.ListenAddrStrings(fmt.Sprintf("/ip4/127.0.0.1/tcp/%d", listenPort)),
+		libp2p.Identity(priv),
+	}
+
+	if !secio {
+		opts = append(opts, libp2p.NoEncryption())
+	}
+
+	basicHost, err := libp2p.New(context.Background(), opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	// Build host multiaddress
+	hostAddr, _ := ma.NewMultiaddr(fmt.Sprintf("/ipfs/%s", basicHost.ID().Pretty()))
+
+	// Now we can build a full multiaddress to reach this host
+	// by encapsulating both addresses:
+	addr := basicHost.Addrs()[0]
+	fullAddr := addr.Encapsulate(hostAddr)
+	log.Printf("I am %s\n", fullAddr)
+	if secio {
+		log.Printf("Now run \"go run main.go -l %d -d %s -secio\" on a different terminal\n", listenPort+1, fullAddr)
+	} else {
+		log.Printf("Now run \"go run main.go -l %d -d %s\" on a different terminal\n", listenPort+1, fullAddr)
+	}
+
+	return basicHost, nil
+}
+
+func handleStream(s net.Stream) {
+
+	log.Println("Got a new stream!")
+
+	// Create a buffer stream for non blocking read and write.
+	rw := bufio.NewReadWriter(bufio.NewReader(s), bufio.NewWriter(s))
+
+	go readData(rw)
+	go writeData(rw)
+
+	// stream 's' will stay open until you close it (or the other side closes it).
+}
+
+func readData(rw *bufio.ReadWriter) {
+
+	for {
+		str, err := rw.ReadString('\n')
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		if str == "" {
+			return
+		}
+		if str != "\n" {
+
+			chain := make([]Block, 0)
+			if err := json.Unmarshal([]byte(str), &chain); err != nil {
+				log.Fatal(err)
+			}
+
+			mutex.Lock()
+			if len(chain) > len(Blockchain) {
+				Blockchain = chain
+				bytes, err := json.MarshalIndent(Blockchain, "", "  ")
+				if err != nil {
+
+					log.Fatal(err)
+				}
+				// Green console color: 	\x1b[32m
+				// Reset console color: 	\x1b[0m
+				fmt.Printf("\x1b[32m%s\x1b[0m> ", string(bytes))
+			}
+			mutex.Unlock()
+		}
+	}
+}
+
+func writeData(rw *bufio.ReadWriter) {
+
+	go func() {
+		for {
+			time.Sleep(5 * time.Second)
+			mutex.Lock()
+			bytes, err := json.Marshal(Blockchain)
+			if err != nil {
+				log.Println(err)
+			}
+			mutex.Unlock()
+
+			mutex.Lock()
+			rw.WriteString(fmt.Sprintf("%s\n", string(bytes)))
+			rw.Flush()
+			mutex.Unlock()
+
+		}
+	}()
+
+	stdReader := bufio.NewReader(os.Stdin)
+
+	for {
+		fmt.Print("> ")
+		sendData, err := stdReader.ReadString('\n')
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		sendData = strings.Replace(sendData, "\n", "", -1)
+		bpm, err := strconv.Atoi(sendData)
+		if err != nil {
+			log.Fatal(err)
+		}
+		newBlock := generateBlock(Blockchain[len(Blockchain)-1], bpm)
+
+		if isBlockValid(newBlock, Blockchain[len(Blockchain)-1]) {
+			mutex.Lock()
+			Blockchain = append(Blockchain, newBlock)
+			mutex.Unlock()
+		}
+
+		bytes, err := json.Marshal(Blockchain)
+		if err != nil {
+			log.Println(err)
+		}
+
+		spew.Dump(Blockchain)
+
+		mutex.Lock()
+		rw.WriteString(fmt.Sprintf("%s\n", string(bytes)))
+		rw.Flush()
+		mutex.Unlock()
+	}
+
+}
+
+func main() {
+	t := time.Now()
+	genesisBlock := Block{}
+	genesisBlock = Block{0, t.String(), 0, calculateHash(genesisBlock), ""}
+
+	Blockchain = append(Blockchain, genesisBlock)
+
+	// LibP2P code uses golog to log messages. They log with different
+	// string IDs (i.e. "swarm"). We can control the verbosity level for
+	// all loggers with:
+	golog.SetAllLoggers(gologging.INFO) // Change to DEBUG for extra info
+
+	// Parse options from the command line
+	listenF := flag.Int("l", 0, "wait for incoming connections")
+	target := flag.String("d", "", "target peer to dial")
+	secio := flag.Bool("secio", false, "enable secio")
+	seed := flag.Int64("seed", 0, "set random seed for id generation")
+	flag.Parse()
+
+	if *listenF == 0 {
+		log.Fatal("Please provide a port to bind on with -l")
+	}
+
+	// Make a host that listens on the given multiaddress
+	ha, err := makeBasicHost(*listenF, *secio, *seed)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if *target == "" {
+		log.Println("listening for connections")
+		// Set a stream handler on host A. /p2p/1.0.0 is
+		// a user-defined protocol name.
+		ha.SetStreamHandler("/p2p/1.0.0", handleStream)
+
+		select {} // hang forever
+		/**** This is where the listener code ends ****/
+	} else {
+		ha.SetStreamHandler("/p2p/1.0.0", handleStream)
+
+		// The following code extracts target's peer ID from the
+		// given multiaddress
+		ipfsaddr, err := ma.NewMultiaddr(*target)
+		if err != nil {
+			log.Fatalln(err)
+		}
+
+		pid, err := ipfsaddr.ValueForProtocol(ma.P_IPFS)
+		if err != nil {
+			log.Fatalln(err)
+		}
+
+		peerid, err := peer.IDB58Decode(pid)
+		if err != nil {
+			log.Fatalln(err)
+		}
+
+		// Decapsulate the /ipfs/<peerID> part from the target
+		// /ip4/<a.b.c.d>/ipfs/<peer> becomes /ip4/<a.b.c.d>
+		targetPeerAddr, _ := ma.NewMultiaddr(
+			fmt.Sprintf("/ipfs/%s", peer.IDB58Encode(peerid)))
+		targetAddr := ipfsaddr.Decapsulate(targetPeerAddr)
+
+		// We have a peer ID and a targetAddr so we add it to the peerstore
+		// so LibP2P knows how to contact it
+		ha.Peerstore().AddAddr(peerid, targetAddr, pstore.PermanentAddrTTL)
+
+		log.Println("opening stream")
+		// make a new stream from host B to host A
+		// it should be handled on host A by the handler we set above because
+		// we use the same /p2p/1.0.0 protocol
+		s, err := ha.NewStream(context.Background(), peerid, "/p2p/1.0.0")
+		if err != nil {
+			log.Fatalln(err)
+		}
+		// Create a buffered stream so that read and writes are non blocking.
+		rw := bufio.NewReadWriter(bufio.NewReader(s), bufio.NewWriter(s))
+
+		// Create a thread to read and write data.
+		go writeData(rw)
+		go readData(rw)
+
+		select {} // hang forever
+
+	}
+}
+
+// make sure block is valid by checking index, and comparing the hash of the previous block
+func isBlockValid(newBlock, oldBlock Block) bool {
+	if oldBlock.Index+1 != newBlock.Index {
+		return false
+	}
+
+	if oldBlock.Hash != newBlock.PrevHash {
+		return false
+	}
+
+	if calculateHash(newBlock) != newBlock.Hash {
+		return false
+	}
+
+	return true
+}
+
+// SHA256 hashing
+func calculateHash(block Block) string {
+	record := strconv.Itoa(block.Index) + block.Timestamp + strconv.Itoa(block.BPM) + block.PrevHash
+	h := sha256.New()
+	h.Write([]byte(record))
+	hashed := h.Sum(nil)
+	return hex.EncodeToString(hashed)
+}
+
+// create a new block using previous block's hash
+func generateBlock(oldBlock Block, BPM int) Block {
+
+	var newBlock Block
+
+	t := time.Now()
+
+	newBlock.Index = oldBlock.Index + 1
+	newBlock.Timestamp = t.String()
+	newBlock.BPM = BPM
+	newBlock.PrevHash = oldBlock.Hash
+	newBlock.Hash = calculateHash(newBlock)
+
+	return newBlock
+}