gop2p

Simple Peer-to-Peer protocol implementation in pure Go. Uses HTTP client and server to communicate over internet to knowed network members.

Download

go get github.com/lucasmenendez/gop2p@latest

Docs & example

• Checkout GoDoc Documentation.
• Also, it is available a simple example that implments a CLI Chat here.

How to use it

The main component to use gop2p is the node.Node struct, that contains:

• Required parameters to handle messages/errors, and connect/disconnect a node.Node:

    type Node struct {
        Self    *peer.Peer    // information about current node
        Members *peer.Members // thread-safe list of peers on the network

        Inbox chan *message.Message // readable channels to receive messages
        Error chan error            // readable channels to receive errors

        Connection chan *peer.Peer       // writtable channel to connect to a Peer
        Outbox     chan *message.Message // writtable channel to send messages
        // ...
    }

• Required functions to create, start and stop a node.Node:

    func New(self *peer.Peer) *Node {
        // ...
    }

    func (node *Node) Start() {
        // ...
    }

    func (node *Node) Stop() error {
        // ...
    }

1. Start a node.Node

To start a new node.Node ad be able to send and receive messages (message.Message) is required to instance a new peer.Peer with the network information (host IP address and port to listen requests).

Show a code example

package main

import (
	"log"

	"github.com/lucasmenendez/gop2p/pkg/node"
	"github.com/lucasmenendez/gop2p/pkg/message"
	"github.com/lucasmenendez/gop2p/pkg/peer"
)

func main() {
    // Instance a new peer that identifies the current node
    self, _ := peer.Me(5001, false)
    // [FOR REMOTE CLIENT] self, _ := peer.Me(5001, true)

    // Create a new node with the self peer defined
    client := node.New(self)

    // Start listening to be able to send and receive messages
    client.Start()

    //...
}

2. Connect to a network and listen fo message.Message or errors

To connect to a network you must know the peer.Peer information of an entrypoint. Use node.Node.Connection channel to connect to it, the node.Node.Inbox channel to listen for messages and the node.Node.Error channel to listen for errors.

Show a code example

package main

import (
	"log"

	"github.com/lucasmenendez/gop2p/pkg/node"
	"github.com/lucasmenendez/gop2p/pkg/message"
	"github.com/lucasmenendez/gop2p/pkg/peer"
)

func main() {
    // ...

    // Create an entry point peer
    entryPoint, _ := peer.Me(5000, false)
    // [REMOTE ENTRYPOINT] entryPoint, _ := peer.New("192.68.1.43", 5000)

    // Connection to the defined entry point peer usign the Connect channel
    client.Connection <- entryPoint

    // Print incoming messages and errors. Every incoming message is populated
    // through Node.Inbox, and every error channel that occurs trough Node.Error
    // channel
    logger := log.New(os.Stdout, "", 0)
    go func(logger *log.Logger) {
        for {
            select {
            case msg := <-client.Inbox:
                logger.Printf("[%s] -> %s\n", msg.From.String(), string(msg.Data))
            case err := <-client.Error:
                logger.Fatalln(err)
            }
        }
    }(logger)

    // ...
}

3. Send message.Message to the network

To broadcast data to the network it must be wrapped using message.Message and the result must be sended using the node.Outbox channel.

Show a code example

package main

import (
	"log"

	"github.com/lucasmenendez/gop2p/pkg/node"
	"github.com/lucasmenendez/gop2p/pkg/message"
	"github.com/lucasmenendez/gop2p/pkg/peer"
)

func main() {
    // ...

    // Create a []byte message
    data := []byte("Hello network!")
    // Create a message with Node.Self information as sender and the created 
    // data
    msg := new(message.Message).SetFrom(client.Self).SetData(data)
    // Broadcast the message to the network putting it into the Node.Outbox 
    // channel
    client.Outbox <- msg

    // ...
}

4. Send a direct message.Message to a single peer

To send data to a single peer network, it must be wrapped using message.Message and its Message.SetTo function, and the result must be sended using the node.Outbox channel.

Show a code example

package main

import (
	"log"

	"github.com/lucasmenendez/gop2p/pkg/node"
	"github.com/lucasmenendez/gop2p/pkg/message"
	"github.com/lucasmenendez/gop2p/pkg/peer"
)

func main() {
    // ...

    // Create a []byte message
    data := []byte("Hello network!")
    // Create a message with Node.Self information as sender, the created data 
    // and de intended peer.
    msg := new(message.Message).SetFrom(client.Self).SetData(data).SetTo(entryPoint)
    // Send the message to defined peer putting it into the Node.Outbox channel
    client.Outbox <- msg

    // ...
}

5. Disconnect from the network

To disconnect from the current network (if the client is already connected to one), the node.Connection channel must be closed. The client node.Node broadcast a disconnection request to every network pee.Peer. The node.Node associated to every pee.Peer, updates its current network member list unregistering the current pee.Peer. At this moment, the current node.Node could connect to other network in any moment (see step 2).

Show a code example

package main

import (
	"log"

	"github.com/lucasmenendez/gop2p/pkg/node"
	"github.com/lucasmenendez/gop2p/pkg/message"
	"github.com/lucasmenendez/gop2p/pkg/peer"
)

func main() {
    // ...

    // Close the Node.Connection channel to disconnect from the network
    close(client.Connection)

    // ...
}

6. Stop the node.Node

To stop the current node.Node the function node.Stop must be executed. This will also disconnect the current node.Node from a network, if it is connected. The function close every channel, stops the HTTP server to stop listening for other peer.Peers requests and stop waiting indifinitely.

Show a code example

package main

import (
	"log"

	"github.com/lucasmenendez/gop2p/pkg/node"
	"github.com/lucasmenendez/gop2p/pkg/message"
	"github.com/lucasmenendez/gop2p/pkg/peer"
)

func main() {
    // ...

    // Stop the Node
    if err := client.Stop(); err != {
        logger.Fatalln(err)
    }
}

Workflow explained

gop2p implements the following functional workflow:

sequenceDiagram
participant Client (Node)
participant Network entrypoint (Node)
participant Network peers (Node)

Note over Client (Node): 1. Start the node
Client (Node) ->> Client (Node): Create and start the client node
Note over Client (Node),Network entrypoint (Node): 2. Connect to the network
Client (Node) ->> Network entrypoint (Node): Send request to known entrypoint (address, port)
Network entrypoint (Node) -->> Network entrypoint (Node): Register a new member
Network entrypoint (Node) -->> Client (Node): Response with the current list of network members
Client (Node) -->> Client (Node): Register all the received members
Client (Node) ->> Network peers (Node): Send connection request
Network peers (Node) -->> Network peers (Node): Register Client as new member

Note over Client (Node),Network peers (Node): 3. Broadcast message
Client (Node) -->> Client (Node): Create the message
Client (Node) ->> Network peers (Node): Broadcast message request to current network Node's

Network peers (Node) -->> Network peers (Node): Handle received Client message

Note over Client (Node),Network peers (Node): 4. Disconnect from the network
Client (Node) -->> Client (Node): Create the disconnect request
Client (Node) ->> Network peers (Node): Broadcast disconnect request to current network Node's

Network peers (Node) -->> Network peers (Node): Unregister Client from current Node's network

Note over Client (Node): 5. Stop the node
Client (Node) ->> Client (Node): Stop the client node