Re: TCP Socket issue - C# Discussion Boards

17-Sep-09 0:43

Hey guys

I'm having some troubles communicating to an external device over the network.

Here's my code

TcpClient BadgerConnection = new TcpClient();
BadgerConnection.Connect(IPAddress.Parse("10.0.0.100"), 1111);

if (BadgerConnection.Connected)
{
    StreamWriter sw = new StreamWriter(BadgerConnection.GetStream());
    sw.AutoFlush = true;

    char[] Buffer = new char[]
    {
        (char)161, // Start Packet
        (char)15,  // Terminal ID
        (char)89,  // Command
        (char)1,   // Amount of arguments to follow
        (char)89,  // Arg 1
        (char)3,   // End Packet
        (char)102  // Checksum = Sum of all chars mod 256
    };

    sw.Write(Buffer);
}

So obviously this isn't working, cause if it did I wouldn't be here Poke tongue | ;-P

What I did was get a packet sniffer and attached it to my program before connecting to the external device.

Here was the result in hex:

C2 A1 0F 59 01 59 03 66

Here's what I intended to send in hex:

A1 0F 59 01 59 03 66

There's an extra character showing up... C2 or rather 194.
Can someone please explain to me why and how can I stop it from sending the extra character?

Thanks

Harvey Saayman - South Africa
Software Developer
.Net, C#, SQL
you.suck = (you.Occupation == jobTitles.Programmer && you.Passion != Programming)
1000100 1101111 1100101 1110011 100000 1110100 1101000 1101001 1110011 100000 1101101 1100101 1100001 1101110 100000 1101001 1101101 100000 1100001 100000 1100111 1100101 1100101 1101011 111111

harold aptroot17-Sep-09 3:17

17-Sep-09 3:17

Odd, I would have expected an UTF-8 BOM, but C2.. that's something else..

Anyway, why are you using chars at all? Why not just bytes?

If you send them as bytes, that should probably get rid of that C2 (at least I never noticed extraneous C2's while sending plain bytes)

Harvey Saayman17-Sep-09 3:26

17-Sep-09 3:26

I tried sending just bytes bytes like so

TcpClient BadgerConnection = new TcpClient();
BadgerConnection.Connect(IPAddress.Parse("10.0.0.100"), 1111);
if (BadgerConnection.Connected)
{
    StreamWriter sw = new StreamWriter(BadgerConnection.GetStream());
    sw.AutoFlush = true;

    byte[] Buffer = new byte[]
    {
        161,
        15,
        89,
        1,
        89,
        3,
        102
    };   
    sw.Write(Buffer);
}

And the sniffer picked up this:

00000000: (TCP/IP) Sending Packet, 17.09.2009 15:24:37.684
BadgerTest.vshost.exe (2188)
0.0.0.0:1200 ® 10.0.0.100:1111
Size: 13 bytes
 53 79 73 74 65 6D 2E 42 79 74 65 5B 5D            System.Byte[]

harold aptroot17-Sep-09 3:30

17-Sep-09 3:30

It seems to be the StreamWriter's fault, what if you send them "normally"?
eg

TcpClient BadgerConnection = new TcpClient();
BadgerConnection.Connect(IPAddress.Parse("10.0.0.100"), 1111);
if (BadgerConnection.Connected)
{
    byte[] Buffer = new byte[]
    {
        161,
        15,
        89,
        1,
        89,
        3,
        102
    };
    NetworkStream ns = BadgerConnection.GetStream();
    ns.Write(Buffer, 0, Buffer.Length);
    ns.Flush();
}

Harvey Saayman17-Sep-09 5:04

17-Sep-09 5:04

That worked like a charm... BUT only the first time Cry | :((

If I try to send that same set of bytes a second time i get an exception

Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host.

Any ideas?

harold aptroot17-Sep-09 5:35

17-Sep-09 5:35

Well, if it were making sense it might mean that the other side did a Close on their Socket
But with networks, sense rarely comes into play Smile | :)

What kind of thing is the remote host? Does it close its socket after any command?

Harvey Saayman17-Sep-09 5:38

17-Sep-09 5:38

harold aptroot wrote:
What kind of thing is the remote host?

Its a proximity card reader

harold aptroot wrote:
Does it close its socket after any command?

Nope, it doesn't Confused | :confused:

harold aptroot17-Sep-09 5:40