> For the complete documentation index, see [llms.txt](https://node1.gitbook.io/node1-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://node1.gitbook.io/node1-docs/solana/fast-landing/udp-api.md).

# UDP API

Send one UDP datagram = one transaction to node1-domain:16888. No handshake, no connection, no response.

> Registration automatically creates an Account UUID and enables Node1 Landing Service at 2 TPS. Use that UUID as the API key in this guide; request higher TPS through Discord.

## Packet

| Offset | Size    | Field    | Value / Note                                                   |
| ------ | ------- | -------- | -------------------------------------------------------------- |
| 0      | 4       | magic    | fixed \[43, 6, 58, 10]                                         |
| 4      | 1       | method   | 0                                                              |
| 5      | 16      | api\_key | your API-key (UUID) as 16 raw bytes, canonical UUID byte order |
| 21     | 2       | tx\_len  | u16 little-endian = number of tx bytes                         |
| 23     | tx\_len | tx       | serialized Solana transaction                                  |

Total length = 23 + tx\_len bytes, sent as one UDP datagram.

## Rules

* tx\_len must not exceed 1232 (a full Solana transaction); larger is rejected.
* No result is returned (fire-and-forget); the server replies nothing. Confirm landing on-chain by the transaction signature.
* One transaction per UDP packet.
* Malformed packets, or packets over your API-key rate limit, are dropped silently (no response means no error is returned).
* Resolve the domain once at startup (connect\_node1 in the example), then only send() on the hot path. Never pass a hostname to send\_to — it does a DNS lookup on every call (milliseconds, measured) and wrecks latency.

## Rust Example

```rust
use std::net::{ToSocketAddrs, UdpSocket};
use uuid::Uuid;

const MAGIC: [u8; 4] = [43, 6, 58, 10];

fn connect_node1(server: &str) -> std::io::Result<UdpSocket> {
    let addr = server
        .to_socket_addrs()?
        .next()
        .ok_or_else(|| std::io::Error::new(std::io::ErrorKind::NotFound, "DNS resolved to nothing"))?;
    let sock = UdpSocket::bind("0.0.0.0:0")?;
    sock.connect(addr)?;
    Ok(sock)
}

fn send_tx(sock: &UdpSocket, api_key: &Uuid, tx_bytes: &[u8]) -> std::io::Result<()> {
    assert!((1..=1232).contains(&tx_bytes.len()), "tx_len must be 1..=1232");
    let mut pkt = Vec::with_capacity(23 + tx_bytes.len());
    pkt.extend_from_slice(&MAGIC);                                  // magic[4]
    pkt.push(0);                                                    // method = 0
    pkt.extend_from_slice(api_key.as_bytes());                     // api_key[16]
    pkt.extend_from_slice(&(tx_bytes.len() as u16).to_le_bytes());  // tx_len[2] little-endian
    pkt.extend_from_slice(tx_bytes);                               // tx[tx_len]
    sock.send(&pkt)?;                                              // fire-and-forget, peer already connected
    Ok(())
}

fn main() -> std::io::Result<()> {
    let sock = connect_node1("fra.node1.me:16888")?;  // resolve once; use the node1 domain you were given
    let api_key = Uuid::parse_str("00000000-0000-0000-0000-000000000000").unwrap(); // your API-key
    let tx_bytes: Vec<u8> = todo!("your serialized transaction");
    send_tx(&sock, &api_key, &tx_bytes)?;
    Ok(())
}
```


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