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Welcome to Software Development on Codidact!

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Comments on Read all data from TCP stream in Rust

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Read all data from TCP stream in Rust

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I'd like to write a TCP client in Rust that can receive the entire message sent by a server, but I have no information about the length of a message.

I'm aware that TCP doesn't preserve message boundaries.

Still, what's the best I can do to read the entire message from the TcpStream?

In the scenario the client should work, there's no protocol for the messages sent from server to client: The client doesn't know beforehand how many bytes are in a message and the message doesn't have a header (as in HTTP) that would contain the message length. There's no special delimiter that marks the end of a message.

Also, the server might keep the TCP connection open after sending a message, meaning I can not rely on every message being completed with a server FIN.

I'd like to do this using Rust's standard library only, no other dependencies.

rust tcp
posted 12 months ago
12mo ago
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Matthias Braun‭
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1 comment thread

There's nothing you can do. It's impossible. Setting a timeout doesn't guarantee the received data i... (5 comments)
There's nothing you can do. It's impossible. Setting a timeout doesn't guarantee the received data i...
__blackjack__‭ wrote 12 months ago
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There's nothing you can do. It's impossible. Setting a timeout doesn't guarantee the received data is a complete message.

Matthias Braun‭ wrote 12 months ago
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The code in the answer I've added (the one setting the timeout) worked for getting the HTML/CSS/JS of a web server and for a custom TCP server that used no protocol. I'm sure there are situations where the 200 ms timeout is too low, so you're right that there's no guarantee to get the whole message. But the code shows that there's something you can do.

__blackjack__‭ wrote 12 months ago
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Yes of course, you can write broken code. And put it on the internet, as an ”answer”, so others can copy that broken code. I think it's a disservice and should not have a place on a Q&A site that aims to curate good, correct, answers. This one isn't even correct. The correct answer to this question isn't code, but that it's impossible.

Matthias Braun‭ wrote 12 months ago
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Can you provide an example server where the code doesn't work? This way, we could improve it or show how it fails.

__blackjack__‭ wrote 12 months ago
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It's not an example server but network infrastructure that may delay traffic for any number of reasons longer than any arbitrary timeout you may define to ”detect” the end of the message.