ReadLine problem

[HalilTorun]

Hello,

I am having a trouble with the ReadLine method in C#. Basically I have a StreamReader (read) attached to a NetworkStream. No problem with this part.

While reading I use the lines below:

string file = "";
string line;
while ((line = read.ReadLine())!= null)
{
file += "\r\n"+line;
}

When I am debug, the code reads till the last line in the network stream. When it attempts to read the last line, debug fails, and interestingly, the window of the form (the lines given above are in the class Form1) appears. Pressing F10, F11 or F5 does not work. In fact they are greyed out in the Debug menu, but Stop Debug, etc still functions.

I think a simple problem but I could not figure it out.

Thank you for helping,

Halil

[r035198x]

1.) I would expect the compiler to whine and say that line may not have been initialized (or similar).
2.) Better use StringBuilder when concatenating strings in a loop. It's more efficient.
3.) What happens when you run the code without any break points?

[Plater]

I would guess that the debug is not broken, but rather that you are not using readline() correct.
ReadLine() is a blocking call so long as their is no "end of stream", which there wouldn't be on a network stream that is still "connected"/"open".
So your debug is stuck sitting there waiting at the ReadLine() command.
If you spaced out your looping mechanism to make it "long winded", you would be able to do step-by-step execution and see that it sits there on the ReadLine() statement.
You will need to code up additional precautions against this.

[r035198x]

..
ReadLine() is a blocking call so long as their is no "end of stream", which there wouldn't be on a network stream that is still "connected"/"open".
...

Missed that one completely.

[HalilTorun]

ReadLine() is a blocking call so long as their is no "end of stream", which there wouldn't be on a network stream that is still "connected"/"open".

Thanks, I understood the reason why it stucks there.

After reading this, I tried another way.

int length = (int)read.BaseStream.Length;
Byte[] fileByte = new Byte[length];
read.BaseStream.Read(fileByte, 0, length);
file += Encoding.ASCII.GetString(fileByte);

When debugger comes to the first line above, an exception is thrown. It says "The stream does not support seek operations".

So, I can not use ReadLine() to read till the end of the file, and also can not use Read() because seek operations are not supported. Do you have any other suggestions about reading the network stream?

[Plater]

You can use read, it's the .Length that you cannot use. Since the stream is still open, there is no "end".
The seek comment was because for .Length to be computed, it needs to read till the end and then come back to the start (using Seeking)

[HalilTorun]

OK, I can use read, but how will I know the length of the file? You know, it requires the number of the bytes to be read as the third parameter. I can give a fixed value but it would not be a good solution.
I feel like reinventing the wheel, how can a file transfer be this hard? :)

[Plater]

Well what protocol are you using to transfer this file? And if it is your own, then you need to create a method for knowing how big the file will be.

[HalilTorun]

I am using the Tcp Protocol.

listen = new TcpListener(System.Net.IPAddress.Any, Convert.ToInt16(textBox1.Text));
listen.Start();
t = new Thread(new ThreadStart(ReadingThread));
t.Start();            

inside ReadingThread I use a socket, and assign a network stream to it, and finally assign a stream reader to the stream.

socket = listen.AcceptSocket();
netStr = new NetworkStream(socket);                
read = new StreamReader(netStr);
 

[Plater]

Ok, so you are making up your own file transfering protocol.
So start it with a header that gives file size, perhaps like

TRANSMISIONSTART
FILETRANSFERHEADER
FILENAME:myfile.tmp
FILESIZE:1024
ENDHEADER


And then you would put 1024 bytes following it that would make up the file size.

Your receive end can read the command header and go ok i read 1024 bytes after the ENDHEADER marker

[HalilTorun]

It really helped.

Thanks