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main.go
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main.go
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package main
import (
"bufio"
"context"
"crypto/rand"
"flag"
"fmt"
"io"
"log"
mrand "math/rand"
"github.com/libp2p/go-libp2p"
"github.com/libp2p/go-libp2p/core/crypto"
"github.com/libp2p/go-libp2p/core/host"
"github.com/libp2p/go-libp2p/core/network"
"github.com/libp2p/go-libp2p/core/peer"
"github.com/libp2p/go-libp2p/core/peerstore"
golog "github.com/ipfs/go-log/v2"
ma "github.com/multiformats/go-multiaddr"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
// 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(golog.LevelInfo) // Change to INFO for extra info
// Parse options from the command line
listenF := flag.Int("l", 0, "wait for incoming connections")
targetF := flag.String("d", "", "target peer to dial")
insecureF := flag.Bool("insecure", false, "use an unencrypted connection")
seedF := 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, *insecureF, *seedF)
if err != nil {
log.Fatal(err)
}
if *targetF == "" {
startListener(ctx, ha, *listenF, *insecureF)
// Run until canceled.
<-ctx.Done()
} else {
runSender(ctx, ha, *targetF)
}
}
// makeBasicHost creates a LibP2P host with a random peer ID listening on the
// given multiaddress. It won't encrypt the connection if insecure is true.
func makeBasicHost(listenPort int, insecure bool, randseed int64) (host.Host, error) {
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 at least
// 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),
libp2p.DisableRelay(),
}
if insecure {
opts = append(opts, libp2p.NoSecurity)
}
return libp2p.New(opts...)
}
func getHostAddress(ha host.Host) string {
// Build host multiaddress
hostAddr, _ := ma.NewMultiaddr(fmt.Sprintf("/p2p/%s", ha.ID()))
// Now we can build a full multiaddress to reach this host
// by encapsulating both addresses:
addr := ha.Addrs()[0]
return addr.Encapsulate(hostAddr).String()
}
func startListener(ctx context.Context, ha host.Host, listenPort int, insecure bool) {
fullAddr := getHostAddress(ha)
log.Printf("I am %s\n", fullAddr)
// Set a stream handler on host A. /echo/1.0.0 is
// a user-defined protocol name.
ha.SetStreamHandler("/echo/1.0.0", func(s network.Stream) {
log.Println("listener received new stream")
if err := doEcho(s); err != nil {
log.Println(err)
s.Reset()
} else {
s.Close()
}
})
log.Println("listening for connections")
if insecure {
log.Printf("Now run \"./echo -l %d -d %s -insecure\" on a different terminal\n", listenPort+1, fullAddr)
} else {
log.Printf("Now run \"./echo -l %d -d %s\" on a different terminal\n", listenPort+1, fullAddr)
}
}
func runSender(ctx context.Context, ha host.Host, targetPeer string) {
fullAddr := getHostAddress(ha)
log.Printf("I am %s\n", fullAddr)
// Turn the targetPeer into a multiaddr.
maddr, err := ma.NewMultiaddr(targetPeer)
if err != nil {
log.Println(err)
return
}
// Extract the peer ID from the multiaddr.
info, err := peer.AddrInfoFromP2pAddr(maddr)
if err != nil {
log.Println(err)
return
}
// We have a peer ID and a targetAddr, so we add it to the peerstore
// so LibP2P knows how to contact it
ha.Peerstore().AddAddrs(info.ID, info.Addrs, peerstore.PermanentAddrTTL)
log.Println("sender 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 /echo/1.0.0 protocol
s, err := ha.NewStream(context.Background(), info.ID, "/echo/1.0.0")
if err != nil {
log.Println(err)
return
}
log.Println("sender saying hello")
_, err = s.Write([]byte("Hello, world!\n"))
if err != nil {
log.Println(err)
return
}
out, err := io.ReadAll(s)
if err != nil {
log.Println(err)
return
}
log.Printf("read reply: %q\n", out)
}
// doEcho reads a line of data a stream and writes it back
func doEcho(s network.Stream) error {
buf := bufio.NewReader(s)
str, err := buf.ReadString('\n')
if err != nil {
return err
}
log.Printf("read: %s", str)
_, err = s.Write([]byte(str))
return err
}