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message-io is a fast and easy-to-use event-driven network library.The library handles the OS socket internally and offers a simple event message API to the user.It also allows you to make an adapter for your own transport protocol following somerules, delegating the tedious asynchrony and thread management to the library.

If you find a problem using the library or you have an idea to improve it,do not hesitate to open an issue.Any contribution is welcome!And remember: morecaffeine, more productive!

Managing sockets is hard because you need to fight with threads, concurrency, full duplex, encoding,IO errors that come from the OS (which are really difficult to understand in some situations), etc.If you make use ofnon-blocking sockets, it adds a new layer of complexity:synchronize the events that come asynchronously from the Operating System.

message-io offers an easy way to deal with all these aforementioned problems,making them transparent for you,the programmer that wants to make an application with its own problems.For that, the library gives you a simple API with two concepts to understand:messages (the data you send and receive), andendpoints (the recipients of that data).This abstraction also offers the possibility to use the same API independentlyof the transport protocol used.You could change the transport of your application in literally one line.

• Highly scalable:non-blocking sockets that allow for the management of thousands of active connections.
• Multiplatform: seemio platform support.
• Multiple transport protocols(docs):
  • TCP: stream and framed mode (to deal with messages instead of stream)
  • UDP, with multicast option
  • WebSocket: plain andsecure#102option usingtungstenite-rs(wasm is not supported butplanned).
• Custom FIFO events with timers and priority.
• Easy, intuitive and consistent API:
  • FollowsKISS principle.
  • Abstraction from transport layer: don't think about sockets, think about messages and endpoints.
  • Only two main entities to use:
    • aNodeHandlerto manage all connections (connect, listen, remove, send) and signals (timers, priority).
    • aNodeListenerto process all signals and events from the network.
  • Forget concurrency problems: handle all connection and listeners from one thread:"One thread to rule them all".
  • Easy error handling:do not deal with dark internalstd::io::Error when sending/receiving from the network.
• High performance (see thebenchmarks):
  • Write/read messages with zero-copy.You write and read directly from the internal OS socket buffer without any copy in the middle by the library.
  • Full duplex: simultaneous reading/writing operations over the same internal OS socket.
• Customizable:message-io doesn't have the transport you need?Easily add anadapter.

• API documentation
• Basic concepts
• Benchmarks
• Examples:
  • Ping Pong (a simple client/server example)
  • Multicast
  • Distributed network with discovery server
  • File transfer
• Open Source applications

Add to yourCargo.toml (all transports included by default):

[dependencies]message-io ="0.19"

If youonly want to use a subset of the available transport battery,you can select them by their associated featurestcp,udp, andwebsocket.For example, in order to include onlyTCP andUDP, add to yourCargo.toml:

[dependencies]message-io = {version ="0.19",default-features =false,features = ["tcp","udp"] }

The following example is the simplest server that reads messages from the clients and respondsto them with the same message.It is able to offer the "service" for 3 differents protocols at the same time.

use message_io::node::{self};use message_io::network::{NetEvent,Transport};fnmain(){// Create a node, the main message-io entity. It is divided in 2 parts:// The 'handler', used to make actions (connect, send messages, signals, stop the node...)// The 'listener', used to read events from the network or signals.let(handler, listener) = node::split::<()>();// Listen for TCP, UDP and WebSocket messages at the same time.    handler.network().listen(Transport::FramedTcp,"0.0.0.0:3042").unwrap();    handler.network().listen(Transport::Udp,"0.0.0.0:3043").unwrap();    handler.network().listen(Transport::Ws,"0.0.0.0:3044").unwrap();// Read incoming network events.    listener.for_each(move |event|match event.network(){NetEvent::Connected(_, _) =>unreachable!(),// Used for explicit connections.NetEvent::Accepted(_endpoint, _listener) =>println!("Client connected"),// Tcp or WsNetEvent::Message(endpoint, data) =>{println!("Received: {}",String::from_utf8_lossy(data));            handler.network().send(endpoint, data);},NetEvent::Disconnected(_endpoint) =>println!("Client disconnected"),//Tcp or Ws});}

The following example shows a client that can connect to the previous server.It sends a message each second to the server and listen its echo response.Changing theTransport::FramedTcp toUdp orWs will change the underlying transport used.

use message_io::node::{self,NodeEvent};use message_io::network::{NetEvent,Transport};use std::time::Duration;enumSignal{Greet,// Any other app event here.}fnmain(){let(handler, listener) = node::split();// You can change the transport to Udp or Ws (WebSocket).let(server, _) = handler.network().connect(Transport::FramedTcp,"127.0.0.1:3042").unwrap();    listener.for_each(move |event|match event{NodeEvent::Network(net_event) =>match net_event{NetEvent::Connected(_endpoint, _ok) => handler.signals().send(Signal::Greet),NetEvent::Accepted(_, _) =>unreachable!(),// Only generated by listeningNetEvent::Message(_endpoint, data) =>{println!("Received: {}",String::from_utf8_lossy(data));},NetEvent::Disconnected(_endpoint) =>(),}NodeEvent::Signal(signal) =>match signal{Signal::Greet =>{// computed every second                handler.network().send(server,"Hello server!".as_bytes());                handler.signals().send_with_timer(Signal::Greet,Duration::from_secs(1));}}});}

Clone the repository and test thePing Pong example(similar to theREADME example but more vitaminized).

Run the server:

cargo run --example ping-pong server tcp 3456

Run the client:

cargo run --example ping-pong client tcp 127.0.0.1:3456

You can play with it by changing the transport, running several clients, disconnecting them, etc.See morehere.

message-io offers twokinds of API.Theuser API that talks tomessage-io itself as a user of the library,and the internaladapter API for those who want to add their protocol adapters into the library.

If a transport protocol can be built in top ofmio(most of the existing protocol libraries can), then you can add it tomessage-ioreally easily:

1. Add youradapter file insrc/adapters/<my-transport-protocol>.rs that implements thetraits that you findhere.It contains only 8 mandatory functions to implement (see thetemplate),and it takes arround 150 lines to implement an adapter.

2. Add a new field in theTransport enum found insrc/network/transport.rs to register your new adapter.

That's all.You can use your new transport with themessage-io API like any other.

Oops! one more step: make aPull Request so everyone can use it :)

• Termchat Terminal chat through the LAN with video streaming and file transfer.
• Egregoria Contemplative society simulation.
• Project-Midas Distributed network based parallel computing system.
• AsciiArena Terminal multiplayer death match game (alpha).
• LanChat LanChat flutter + rust demo.

Does your awesome project usemessage-io? Make a Pull Request and add it to the list!

message-io has the main goal to keep things simple.This is great, but sometimes this point of view could make more complex the already complex things.

For instance,message-io allows handling asynchronous network events without using anasync/await pattern.It reduces the complexity to handle income messages from the network, which is great.Nevertheless, the applications that read asynchronous messages tend to performasynchronous tasks over these events too.This asynchronous inheritance can easily be propagated to your entire applicationbeing difficult to maintain or scale without an async/await pattern.In those cases, maybetokio could be a better option.You need to deal with more low-level network stuff but you gain in organization and thread/resource management.

A similar issue can happen regarding the node usage ofmessage-io.Because a node can be used independently as a client/server or both,you can easily start to make peer to peer applications.In fact, this is one of the intentions ofmessage-io.Nevertheless, if your goal scales, will appear problems related to this patter to deal with,and libraries such aslibp2p come with a huge battery of tools to help to archive that goal.

Of course, this is not a disclaiming about the library usage (I use it!),it is more about being honest about its capabilities,and to guide you to the right tool depending on what are you looking for.

To summarize:

• If you have a medium complex network problem: make it simpler withmessage-io!
• If you have a really complex network problem: usetokio,libp2p or others, to have more control over it.