将Node.js net.socket与流消息协议一起使用

Question

I have a C++ server process I'm trying to connect to over TCP which uses a simple stream protocol. The first 8 bytes of the packet is the message length in bits and then the rest of the packet is the actual message as a string. A C++ client process which connects to said server constructs messages for it like this:

char* msgBuff = new char[msgLen + sizeof(int)];
int nlen = htonl(msgLen);
memcpy(msgBuff, &nlen, sizeof(int));
memcpy(msgBuff + sizeof(int), msg, msgLen);

So I'm trying to do the same in node.js. I have my message string and I wrote my own version of htonl by converting a msglen var into a string representing the correct byte swapped hex value. Then I do parseInt with that string to get the var as a hex value:

var byteSwappedMsgLen = parseInt(lengthAsAString,16);

And then I try to write this and my msg to my net.socket like this:

soc.write(byteSwappedMsgLen + msg);

But something is wrong. My msg length of 210 which is 000000d2 in hex gets byteswapped by my function so that lengthAsAString=d2000000. But for some reason when I print byteSwappedMsgLen to the console it's equal to 3523215360. The C++ server reads it as a message length of 859124275. So I'm not sure if I'm not converting the string correctly and\\or if I'm not constructing the message properly.

Answer 1

Figured out I need to use Buffers and pad the hex value with leading zeros (no need to byte swap).

var buffer = new Buffer(msg.length + 4);
buffer.write(paddy(msg.length.toString(16),8),'hex');
buffer.write(msg,4,'ascii');
s.write(buffer);

//found this function elsewhere
function paddy(n, p, c) {
    var pad_char = typeof c !== 'undefined' ? c : '0';
    var pad = new Array(1 + p).join(pad_char);
    return (pad + n).slice(-pad.length);
}