submitted 1 month ago* (last edited 1 month ago) by SpiderUnderUrBed@lemmy.zip to c/rust@programming.dev

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Hello, I am starting to learn and play around with tokio and multithreaded code. I am now playing around with websockets, I don't quite understand the difference between broadcast and mpsc, and when would you use either, I mean, I am assuming broadcast is intended for multiple clients, but multiple clients were able to connect to my mscp channel, and receive a bit of data (but it was weird and partial). So I don't quite get it.

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[-] TehPers@beehaw.org 5 points 1 month ago

Tokio's broadcast module is a mpmc messaging queue.

The terms "mpsc" and "mpmc" refer to how the channels can be used. Breaking down the letters, there are two sides to a channel:

p is producer, or transmitter/sender. This side sends data
c is consumer, or receiver/reader. This side receives data.

Data only flows one way through a channel. Each side may have a restriction on how many members can be on that side:

s is single, so this side cannot be cloned. You only have one object that can interact with this side (so only one sender or only one receiver)
m is multiple, so this side can be cloned. Any number of objects can exist that interact with this side (so a bunch of simultaneous senders or receivers)

A mpsc channel can only have one consumer, so only one thread can receive messages at a time, and it can only receive those messages once.

A mpmc channel can have many consumers, so multiple threads can receive messages at once, and a thread can receive a message multiple times (through multiple receivers).

Both can have multiple simultaneous producers.