@Override
    public long writeTo(TransferableChannel channel) throws IOException {
        long written = channel.write(buffers);
        if (written < 0)
            throw new EOFException("Wrote negative bytes to channel. This shouldn't happen.");
        remaining -= written;
        pending = channel.hasPendingWrites();
        return written;
    }
A send backed by an array of byte buffers
clients/src/main/java/org/apache/kafka/common/network/ByteBufferSend.java