What is mplex?

mplex is a simple stream multiplexer that was designed in the early days of libp2p. It is a simple protocol that does not provide many features offered by other stream multiplexers. Notably, mplex does not provide flow control, a feature which is now considered critical for a stream multiplexer.

mplex runs over a reliable, ordered pipe between two peers, such as a TCP connection. Peers can open, write to, close, and reset a stream. mplex uses a message-based framing layer like yamux, enabling it to multiplex different data streams, including stream-oriented data and other types of messages.


mplex does not have any flow control.

Backpressure is a mechanism to prevent one peer from overwhelming a slow time consuming the data.

mplex also doesn’t limit how many streams a peer can open.