Will `TcpStream` be disabled once it receives an invalid UTF-8?

Question

I'm trying to create a server that receives a string from a client through TCP socket communication and returns the same string to the same socket. I want the following specifications:

• Repeat communication with the client (corresponding to the loop block in the code below)
• When the client receives a valid UTF-8 character, return the same character ( Ok branch in the loop block)
• When the client does not receive a valid UTF-8 character, return the string "Invalid data" ( Err branch in the loop block)

use std::io::Error;
use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
use tokio::net::TcpListener;

#[tokio::main]
async fn main() -> Result<(), Error> {
    // Create TCP listener
    let addr = "localhost:8080";
    let socket = TcpListener::bind(&addr).await;
    let listener = socket.unwrap();

    // Accept connection
    let (mut socket, _addr) = listener.accept().await.unwrap();

    // Split socket into read and write halves
    let (reader, mut writer) = socket.split();

    // Read buffer into string
    let mut line = String::new();
    let mut buf_reader = BufReader::new(reader);
    loop {
        match buf_reader.read_line(&mut line).await {
            Ok(bytes) => {
                if bytes == 0 {
                    // `bytes == 0` means the connection is closed 
                    break;
                }
            }
            Err(error) => {
                println!("{error}");
                line = "Invalid data".to_string();
            }
        }
        // Respond to client
        writer.write_all(line.as_bytes()).await.unwrap();
        line.clear();
    }

    Ok(())
}

The client is te.net on macOS.

telnet localhost 8080

Below are how to reproduce the issue:

• Typing "hello" returns "hello" .
• Typing ctrl-C and pressing Enter shows "stream did not contain valid UTF-8" on the server side and no response from the server is displayed on the te.net side (I want "Invalid data" to be displayed).
• Typing "hello" again returns nothing, even though I have confirmed that the server is receiving it.

te.net output:

hello
hello
^C
hello

Will the TcpStream become invalid once invalid UTF-8 is received?

Expected behaviours

• The server returns " Invalid data " when it receives invalid UTF-8 characters.
• The server returns the same characters it receives if they are valid UTF-8 characters, even after receiving invalid UTF-8 characters in the previous loop .

Answer 1

It was an issue with te.net . I created invalid.csv which contains 3 rows alternating between valid and invalid rows of UTF-8 sequences:

invalid.csv

hello
(invalid UTF-8 sequences)
hello

Then, I used a pipe with nc command:

cat invalid.csv | nc localhost 8080

The output was:

hello
Invalid data
hello

which is as expected.