Function drain

src/upstreamproxy/relay.ts:215–226

(sock)

        handleData(adapter, st, data, wsUrl, authHeader, wsAuthHeader)
      },
      drain(sock) {
        const st = sock.data
        while (st.writeBuf.length > 0) {
          const chunk = st.writeBuf[0]!
          const n = sock.write(chunk)
          if (n < chunk.length) {
            st.writeBuf[0] = chunk.subarray(n)
            return
          }
          st.writeBuf.shift()
        }
      },
      close(sock) {
        cleanupConn(sock.data)
      },