send a binary json message to a tcp server in rust

To send a binary json message to a tcp server in Rust, first you need to serialize the data you want to send using the serde_json crate. Then you need to convert the serialized data into a binary format and send it to the server over a TCP connection using the std::net::TcpStream type.

Here is an example of how you can achieve this:

main.rs
use serde_derive::{Serialize, Deserialize};
use serde_json::{to_vec};
use byteorder::{WriteBytesExt, BigEndian};
use std::io::prelude::*;
use std::net::TcpStream;

#[derive(Serialize, Deserialize)]
struct Message {
    id: u32,
    payload: String
}

fn send_message(msg: &Message) -> std::io::Result<()> {
    let mut stream = TcpStream::connect("127.0.0.1:8080")?;

    // serialize the message to binary json format
    let serialized_msg = to_vec(&msg).unwrap();

    // write the length of the serialized message as a 4-byte integer
    stream.write_u32::<BigEndian>(serialized_msg.len() as u32)?;

    // write the serialized message
    stream.write_all(&serialized_msg)?;

    Ok(())
}

fn main() {
    let msg = Message {
        id: 1,
        payload: "Hello, world!".to_string()
    };

    send_message(&msg).unwrap();
}
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In this example, we first define a Message struct using the serde_derive macro. We then use the serde_json::to_vec function to serialize the msg object of our message struct to a binary json format.

We then create a TCP stream to the server using the TcpStream::connect method. We write the length of the serialized message as a 4-byte integer using the WriteBytesExt::write_u32 method, and then write the serialized message itself using the Write::write_all method of the TcpStream.

Finally, we call the send_message function with our msg object to send the message to the server.

Note that this is just an example, and in a real-world application, you may want to handle errors and timeouts properly, and also use a more robust serialization format like protobuf or capnproto.