How to Send Data from Rust to JS

[Zedonboy]

I have a Rust libp2p connecting to browser node through relay, i try to use request-response, but i get

Stream event: OutboundFailure { peer: PeerId("12D3KooWGffVBgszhdzsyKRx2aRiNQno3KwCmFyPBHmgjdgNk11L"), connection_id: ConnectionId(1), request_id: OutboundRequestId(1), error: Io(Custom { kind: UnexpectedEof, error: Eof { name: "array", expect: Small(1) } }) }

The Js side listens for data. libp2p.handle("/protocol/1.0.0", ....)

How do i reliably send data?

[jxs]

Hi, and thanks for your interest! Did you see #6038?

[Zedonboy]

I checked the thread, i didn't see any solution.

[elenaf9]

Do you check the request and response sizes, as mentioned in #6038?

[Zedonboy]

I don't know how to check request and response sizes.

I check the docs, i cant see any function like that. can you show me a sample.

i use libp2p v0.55.0, with "request-response" feature

[elenaf9]

I don't know how to check request and response sizes.

How do the <Request, Response> structures look like that you are sending/ receiving? Max request size is per default 1MiB, max response is 10MiB, for both cbor and json.
Also, are using the exact same codec (i.e. cbor or json) as the js side? I am not really familiar with their implementation of the request-response protocol.

[Zedonboy]

i used cbor
Send test data type "Hello world"
I don't know of any Js request-response, the closest i got is jsnode.handle("protocol" cb)

here's the initialization
`pub async fn create_swarm(keypair: &Keypair) -> Result<Swarm, Box> {

let swarm = SwarmBuilder::with_existing_identity(keypair.clone())
.with_tokio()
.with_websocket(
    (libp2p::tls::Config::new, libp2p::noise::Config::new),
    libp2p::yamux::Config::default,
).await?
.with_relay_client(
    (libp2p::tls::Config::new, libp2p::noise::Config::new),
    libp2p::yamux::Config::default,
)?
.with_behaviour(|key, relay|
    
    NodeBehaviour {
        relay,
        ping: ping::Behaviour::new(Config::default()),
        identify: identify::Behaviour::new(libp2p::identify::Config::new(
            "1.0.0".to_string(), keypair.public())),
        stream: request_response::cbor::Behaviour::new(
            [(
                libp2p::StreamProtocol::new("/echo/1.0.0"),
                libp2p::request_response::ProtocolSupport::Full,
            )],
            request_response::Config::default(),
        ),
        super_stream: libp2p_stream::Behaviour::new()
        
    })?
    .build();

Ok(swarm)

}`

here's the usage
swarm.behaviour_mut().stream.send_request(&peer_id, FileRequest("Hellok".to_string()));

[elenaf9]

I don't know of any Js request-response, the closest i got is jsnode.handle("protocol" cb)

That's quite important. The EOF error occurs because the remote peer (in your case the js side) doesn't reply with any response but instead closes the stream. Why that happens depends on the js logic.

One easy explanation could be that a different protocol name (i.e. different from "/echo/1.0.0") is used by js. But if that's not the reason then some more insights on the js side are needed.

[elenaf9]

dialing a public jsnode to be used as relay, how do get the relay connection address(the one with "p2p-circuit" )

You don't need to dial the relay node manually. Just call Swarm::listen_on on the relayed address <relay_addr>/p2p/<relay_id>/p2p-circuit/<own_id>

[Zedonboy]

Thanks for your assistance so far. The protocol is a typo.(Whenever there's protocol mismatch is get Protocol Unsupported error) thats isn't the case here.

1. I suspect that Jsnode and rustnode may not be compatible.

2. I used WASM instead, i did Swarm listen on <relay addr>/p2p-circuit/p2p/<peer id>

3. I get these events ConnectionEstablished to relay id
   and
   RelayReservationEstablished

4. In another node(rust) i tried dialing directly to <relay addr>/p2p-circuit/<remote peer id>

5. It gets connected to Relay only(received ConnectionEstablished event)

It doesn't get connected to the end node.

Neither show any events of connection establishment.

What could be the cause?

[Zedonboy]

@elenaf9 I made sure every node is running rust libp2p

here's my logs. same error

Peer Id: PeerId("12D3KooWQbb8sgML5CmE34Bzr2DveY3GAzQq8ycv81AYYnxN3fBu")
Starting loop
2025-06-11T21:15:37.467590Z  INFO ThreadId(01) src/main.rs:64: Connected to the listening node 12D3KooWGB8FedbRvQjAGwWN6V33SmzjrB3PKVbV9wEbS617dHaM
2025-06-11T21:15:38.287663Z  INFO ThreadId(01) src/main.rs:81: Relay event: OutboundCircuitEstablished { relay_peer_id: PeerId("12D3KooWGB8FedbRvQjAGwWN6V33SmzjrB3PKVbV9wEbS617dHaM"), limit: Some(Limit { duration: Some(120s), data_in_bytes: Some(131072) }) }
2025-06-11T21:15:38.659956Z  INFO ThreadId(01) src/main.rs:64: Connected to the listening node 12D3KooWE4xWpJhko1RyWFG82LQuHdGYLAms68YUTAaaY8MbHXjX
2025-06-11T21:15:38.660024Z  INFO ThreadId(01) src/main.rs:67: we dialed this node
Sent data
2025-06-11T21:15:39.952027Z  INFO ThreadId(01) src/main.rs:85: Stream event: OutboundFailure { peer: PeerId("12D3KooWE4xWpJhko1RyWFG82LQuHdGYLAms68YUTAaaY8MbHXjX"), connection_id: ConnectionId(1), request_id: OutboundRequestId(1), error: Io(Custom { kind: UnexpectedEof, error: Eof { name: "array", expect: Small(1) } }) }

Here's my implementation

pub async fn create_swarm(keypair: &Keypair) -> Result<Swarm<NodeBehaviour>, Box<dyn std::error::Error>> {
    
    let swarm = SwarmBuilder::with_existing_identity(keypair.clone())
    .with_tokio()
    .with_websocket(
        (libp2p::tls::Config::new, libp2p::noise::Config::new),
        libp2p::yamux::Config::default,
    ).await?
    .with_relay_client(
        libp2p::noise::Config::new,
        libp2p::yamux::Config::default,
    )?
    .with_behaviour(|key, relay|
        
        NodeBehaviour {
            relay,
            ping: ping::Behaviour::new(Config::default()),
            identify: identify::Behaviour::new(libp2p::identify::Config::new(
                "1.0.0".to_string(), keypair.public())),
            stream: request_response::cbor::Behaviour::new(
                [(
                    libp2p::StreamProtocol::new("/fusion/1.0.0"),
                    libp2p::request_response::ProtocolSupport::Full,
                )],
                request_response::Config::default(),
            ),
            super_stream: libp2p_stream::Behaviour::new(),
            dcutr: libp2p::dcutr::Behaviour::new(key.public().to_peer_id())
            
        })?
        .build();

    Ok(swarm)
}

how do i change the response sizes

[Zedonboy]

I Found a Solution.

1. Js and Rust libp2p subsytems are not compatible. You use 1 runtime for all your node types Listener and Dialer.
2. but if you must use JS, then use Rust Wasm
3. Io(Custom { kind: UnexpectedEof, error: Eof { name: "array", expect: Small(1) } }) } Error in my case means that the Receiver dnt send back a response.

If you get this error, make sure they are using the StreamProtocol name and make sure both nodes are recieving Outbound and Inbound Events.

Thank you for your response.
@jxs @elenaf9