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package p2p
import (
"bufio"
"encoding/json"
"errors"
"fmt"
"net"
"sync"
"time"
"go.uber.org/zap"
)
// `Message` represents a structured message on this network.
type Message struct {
Timestamp int64 `json:"timestamp"`
Source string `json:"source"`
Payload []byte `json:"payload"`
}
// A network ID is represented by a string
type NetworkID string
// This type represents the function that is called every time a new message
// arrives to the server.
type NetworkMessageReceiveFunc func(msg Message)
// This type represent the callback function invokes every new handshake between
// two peers
type NetworkHandshakeFunc func() error
func DefaultHandshake() error {
return nil
}
// Network options to define on new `TCPNetwork`
type TCPNetworkOpts struct {
ListenAddr string
RetryDelay time.Duration
HandshakeFn NetworkHandshakeFunc
OnReceiveFn NetworkMessageReceiveFunc
Logger *zap.Logger
}
// TCPNetwork represents a full-duplex TCP peer.
type TCPNetwork struct {
sync.Mutex
TCPNetworkOpts
id NetworkID
listener net.Listener
connections map[NetworkID]net.Conn
}
// Initiliaze a new TCP network
func NewTCPNetwork(localID NetworkID, opts TCPNetworkOpts) *TCPNetwork {
n := &TCPNetwork{
TCPNetworkOpts: opts,
id: localID,
connections: make(map[NetworkID]net.Conn),
}
go n.startServer()
return n
}
// Close listener' connection
func (n *TCPNetwork) Close() error {
return n.listener.Close()
}
// Add a new peer connection to the local peer
func (n *TCPNetwork) AddPeer(remoteID NetworkID, addr string) {
go n.retryConnect(remoteID, addr)
}
// Send methods is used to send a message to a specified remote peer
func (n *TCPNetwork) Send(remoteID NetworkID, payload []byte) error {
n.Lock()
conn, exists := n.connections[remoteID]
n.Unlock()
if !exists {
return fmt.Errorf("not connected to peer %s", remoteID)
}
msg := Message{
Payload: payload,
Source: n.listener.Addr().String(),
Timestamp: time.Now().Unix(),
}
data, err := json.Marshal(msg)
if err != nil {
return fmt.Errorf("failed to marshal message: %v", err)
}
_, err = conn.Write(append(data, '\n'))
if err != nil {
n.Logger.Sugar().Errorf("failed to send message to %s: %v. Reconnecting...", remoteID, err)
n.Lock()
delete(n.connections, remoteID)
n.Unlock()
go n.retryConnect(remoteID, "")
return fmt.Errorf("failed to send message: %v", err)
}
return nil
}
// RegisterHandler registers a callback for a message type.
func (n *TCPNetwork) RegisterHandler(callback NetworkMessageReceiveFunc) {
n.OnReceiveFn = callback
}
// startServer starts a TCP server to accept connections.
func (n *TCPNetwork) startServer() error {
var err error
n.listener, err = net.Listen("tcp", n.ListenAddr)
if err != nil {
n.Logger.Sugar().Errorf("failed to start server: %v", err)
return err
}
go n.listenLoop()
n.Logger.Sugar().Infof("server started on %s\n", n.ListenAddr)
return nil
}
func (n *TCPNetwork) listenLoop() error {
for {
conn, err := n.listener.Accept()
if errors.Is(err, net.ErrClosed) {
n.Logger.Sugar().Errorf("connection is closed in such a way: %v\n", err)
return err
}
if err != nil {
n.Logger.Sugar().Errorf("failed to accept connection: %v\n", err)
continue
}
remoteAddr := conn.RemoteAddr().String()
n.Lock()
n.connections[NetworkID(remoteAddr)] = conn
if err := n.HandshakeFn(); err != nil {
n.Logger.Sugar().Errorf("error on handshaking: %v\n", err)
return err
}
n.Unlock()
n.RetryDelay = 2 * time.Second
n.Logger.Sugar().Infof("connected to remote peer %s\n", remoteAddr)
// Read loop
go n.listenForMessages(conn)
}
}
// listenForMessages listens for incoming messages.
func (n *TCPNetwork) listenForMessages(conn net.Conn) {
reader := bufio.NewReader(conn)
for {
data, err := reader.ReadBytes('\n')
if err != nil {
n.Logger.Debug("connection lost. Reconnecting...")
n.Lock()
// FIXME: a better way to re-establish the connection between peer
for id, c := range n.connections {
if c == conn {
delete(n.connections, id)
go n.retryConnect(id, "")
break
}
}
n.Unlock()
return
}
var message Message
if err := json.Unmarshal(data, &message); err != nil {
n.Logger.Sugar().Errorf("failed to unmarshal message: %v\n", err)
continue
}
n.Logger.Sugar().Infof("Received message from '%s': %s", message.Source, string(message.Payload))
n.OnReceiveFn(message)
}
}
// retryConnect attempts to connect to a remote peer.
func (n *TCPNetwork) retryConnect(remoteID NetworkID, addr string) {
for {
n.Lock()
_, exists := n.connections[remoteID]
n.Unlock()
if exists {
time.Sleep(5 * time.Second)
continue
}
conn, err := net.Dial("tcp", addr)
if err != nil {
n.Logger.Sugar().Errorf("failed to connect to %s: %v. Retrying in %v...", remoteID, err, n.RetryDelay)
time.Sleep(n.RetryDelay)
if n.RetryDelay < 30*time.Second {
n.RetryDelay *= 2
} else {
n.Lock()
delete(n.connections, remoteID)
n.Unlock()
n.Logger.Sugar().Infof("removed %s connection", remoteID)
return
}
continue
}
n.Lock()
n.connections[remoteID] = conn
n.Unlock()
n.Logger.Sugar().Infof("successfully connected to peer %s!", remoteID)
go n.listenForMessages(conn)
}
}
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