C# Sending Hex string to tcp socket

Question

I'm trying to send a hex string to a tcp socket. I have some problems with the format or conversion of this string, cause I'm not very sure what the format its using.

I've written a WindowsPhone app which is working fine based on Socket Class. This app emulates request, that are normaly send from a desktop program to a device which hosts a webservice.

Via wireshark, I found out, that the webservice will accept an input stream (think its in hex) and returns a 2nd. hex stream which contains the data I need.

So the desktop app is sending a stream and Wireshark shows when :

Data (8 bytes) Data: 62ff03fff00574600 Length: 8

Now I've tried a lot to reproduce this stream. I thougt, it used to be a UTF8 string and converted this stream to this format. But every time I send it, is see in Wireshark the following output: 62c3bf03c3bf00574600

As far as i've investigated 62 = b but ff send always c3bf.

Does somebody know how to send this stream in the right format?

Cheers, Jo

Answer 1

The socket transport shouldn't care, the content of a TCP packet is binary representing "whatever". From the code you pointed to in the comments:

byte[] payload = Encoding.UTF8.GetBytes(data);
socketEventArg.SetBuffer(payload, 0, payload.Length);
...
response = Encoding.UTF8.GetString(e.Buffer, e.Offset, e.BytesTransferred);
response = response.Trim('\0');

At the end of the socket send/receive (data == response). If that isn't occurring you need to figure how where the problem is. The first step is to write some very simple code like so:

string source = "your problem text string";
byte[] encode = Encoding.UTF8.GetBytes(source);
target = Encoding.UTF8.GetString(encode, 0, encode.Length);
Debug.Assert(source == target);

If that works, then output the 'encode' array can check to make sure that is contained in the packet data where it is being send, then verify that that is what is being received. If you are sending the right data but receiving it corrupted you have serious problems ... I doubt you find that but if so write a very simple test program that sends and receives on the same machine (localhost) to see if it is repeatable.

If I had to guess I would say that the characters being encoded are not Unicode or that Win phone doesn't properly support it (Proper unicode support).

Answer 2

As long as you don't know the protocol / the encoding the server expects you can only replay the known messages, like the bytes you provided in your question.

Therefore you just define directly the byte array like this:

byte[] payload = new byte[] {0x62, 0xff, 0x03, 0xff, 0xf0, 0x05, 0x74, 0x60};

and send it over the socket like you did with the encoded string before. The server should now accept the message like it was sent by the client you sniffed.