# cmux: Connection Mux ![Travis Build Status](https://api.travis-ci.org/soheilhy/args.svg?branch=master "Travis Build Status") [![GoDoc](https://godoc.org/github.com/soheilhy/cmux?status.svg)](http://godoc.org/github.com/soheilhy/cmux)

cmux is a generic Go library to multiplex connections based on
their payload. Using cmux, you can serve gRPC, SSH, HTTPS, HTTP,
and Go RPC on the same TCP listener to avoid using one port per
protocol.

## How-To
Simply create your main listener, create a cmux for that listener,
and then match connections:
```go
// Create the main listener.
l, err := net.Listen("tcp", ":23456")
if err != nil {
	log.Fatal(err)
}

// Create a cmux.
m := cmux.New(l)

// Match connections in order:
// First grpc, then HTTP, and otherwise Go RPC/TCP.
grpcL := m.Match(cmux.HTTP2HeaderField("content-type", "application/grpc"))
httpL := m.Match(cmux.HTTP1Fast())
trpcL := m.Match(cmux.Any()) // Any means anything that is not yet matched.

// Create your protocol servers.
grpcS := grpc.NewServer()
grpchello.RegisterGreeterServer(grpcs, &server{})

httpS := &http.Server{
	Handler: &helloHTTP1Handler{},
}

trpcS := rpc.NewServer()
s.Register(&ExampleRPCRcvr{})

// Use the muxed listeners for your servers.
go grpcS.Serve(grpcL)
go httpS.Serve(httpL)
go trpcS.Accept(trpcL)

// Start serving!
m.Serve()
```

Take a look at [other examples in the GoDoc](http://godoc.org/github.com/soheilhy/cmux/#pkg-examples).

## Docs
* [GoDocs](https://godoc.org/github.com/soheilhy/cmux)

## Performance
There is room for improvment but, since we are only matching
the very first bytes of a connection, the performance overheads on
long-lived connections (i.e., RPCs and pipelined HTTP streams)
is negligible.

*TODO(soheil)*: Add benchmarks.

## Limitations
* *TLS*: Since `cmux` sits in between the actual listener and the mux'ed
listeners, TLS handshake is not handled inside the actual servers.
Because of that, you can serve HTTPS using cmux but `http.Request.TLS`
would not be set in your handlers.

* *Different Protocols on The Same Connection*: `cmux` matches the connection
when it's accepted. For example, one connection can be either gRPC or REST, but
not both. That is, we assume that a client connection is either used for gRPC
or REST.