andrinheusser•2y ago

Sequentially write to TPC connection

Hey, I experience errors when multiple async functions write to a TCP (Deno.Conn) connection. How can I make sure my data is sent fully, even if it can't be written to the send buffer in one function call? Using this code, I observed data (buf) being written partially, then data from other async functions being written before the remainder of the partially written data is written.

        const id = (Math.random() + 1).toString(36).substring(7);
        let nwritten = 0;
        let pass = 0;
        while (nwritten < buf.byteLength) {
          console.log(id, pass - 1, 'starting pass ', pass, { nwritten, length: buf.byteLength })
    
          nwritten += await this.#conn.write(buf.subarray(nwritten));
    
          console.log(id, pass, ' written: ' + `${nwritten} / ${buf.byteLength}`);
          pass++;
        }
        console.log(id, pass, ' fininshed writing: ' + nwritten + ' / ' + buf.length)

        const id = (Math.random() + 1).toString(36).substring(7);
        let nwritten = 0;
        let pass = 0;
        while (nwritten < buf.byteLength) {
          console.log(id, pass - 1, 'starting pass ', pass, { nwritten, length: buf.byteLength })
    
          nwritten += await this.#conn.write(buf.subarray(nwritten));
    
          console.log(id, pass, ' written: ' + `${nwritten} / ${buf.byteLength}`);
          pass++;
        }
        console.log(id, pass, ' fininshed writing: ' + nwritten + ' / ' + buf.length)

2 Replies

AapoAlas•2y ago

Std at least has some APIs named to "writeAll" which may be relevant.

andrinheusser•2y ago

Yes, this "heavily inspired" the code included in the post. It's basically the same minus console.log.