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Re: Opening large files / sockets

11-Sep-07 12:22

I made a simple program to send files over a socket.
Its very simple, it opens the file, reads 100Kb, then sends it across, reads the next 100Kb and sends it. At the other end each 100Kb chunk is written to file as it arrives.

I sent across a 10KB file, 77MB file, with no problems. Then i came to send a rather large file... just over 4GB. I'll need to investigate more, but from what i can see the file is opened, the connection is made but it fails to send the first chunk, the recipient just sits there waiting for data to arrive.

Im unsure of where the problem might be, or what would cause it. If anyone could shed some light on the subject i'd be very grateful.

-- modified at 19:26 Tuesday 11th September, 2007
Hmm, okay file length in bytes is 4,294,967,296. To big to fit in an int right? That might be the problem. Then again, the only thing using int's is the progress bar.

-- modified at 20:45 Tuesday 11th September, 2007

Luc Pattyn11-Sep-07 13:25

Luc Pattyn

11-Sep-07 13:25

Hi, I would guess you are having a 32-bit/64-bit problem.
Are you using longs (i.e. 64-bit) for all lengths and offsets?
you are aware array indexing is using ints, are you?

Smile | :)

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Re: Opening large files / sockets [modified]

Anthony Mushrow11-Sep-07 13:37

Re: Opening large files / sockets

11-Sep-07 13:37

Yeah, from what i can see there shouldn't be a problem.

Send:

if((currentFile.Length-currentFile.Position) < PacketSize)<br />
    count = (int)currentFile.Length-(int)currentFile.Position;<br />
else<br />
    count = PacketSize;<br />
<br />
currentFile.Read(Data, 0, count);<br />
ServerConnection.Send(Data);<br />
ServerConnection.Receive(OK);

Recieve:

Rx = ClientConnection.Receive(Data);<br />
FS.Write(Data,0,Rx);<br />
ClientConnection.Send(OK);

Thats pretty much the bare bones of it. Using count makes sure i don't send a load of blank data at the end of the file, and it would only be set by calculating the difference between the length and position when this difference is less than the size of each chunk, so that would easily fit into an int.

Edit: *slaps self* Ouch, i got it, further up the code, i send a packet with some file information, Name, filesize etc. The other person then gets a message asking them if they want to accept the file. The filesize is currently stored as a 32-bit int. The person sending the file is gonna crash right there. Although no error message is given, or any indication something has gone wrong.

-- modified at 19:49 Tuesday 11th September, 2007
Damn, still fails to send the first peice of the file. Although im one stpe closer, previously it got stuck trying to parse the 64-bit file length from a string into a 32-bit int. Now it gets stuck err... just after? More investigation required.

-- modified at 19:57 Tuesday 11th September, 2007
Secrets Revealed. The first chunk is sent, i check the downloads folder, and sitting there is a few KB of the 4GB file, in all its glory.

Luc Pattyn11-Sep-07 14:04

Luc Pattyn

11-Sep-07 14:04

The code snippets shown don't help at all, since all declarations are missing.
What is the type of currentFile, PacketSize, Data, etc?
what is the size of Data, the value of PacketSize?

Where is the try-catch, are you getting any exception?
Did you care to look at the value of count?

Communication (and interfacing in general) must be implemented in a very defensive way:
whatever can conceivably go wrong will sooner or later go wrong, so make provisions for
the worst case right from the start!

Smile | :)

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Re: Opening large files / sockets

Anthony Mushrow11-Sep-07 14:20

Re: Opening large files / sockets [solved]

11-Sep-07 14:20

currentFile is a FileStream, opened with File.Open(path, FileMode.Open);
PacketSize is an int currently at 512KB (524288 bytes)
Data is an array of bytes the same length as the PacketSize (except in the case of sending, when the remaining data is smaller than 512KB)

There is no try catch, and i cant test right now so i'll have to wait until tommorow to add stuff in and check.

count comes out fine, although there will be problems at the end of the file, because the file length will have been shortened to the maximun size of an int as will the current position, end result, count is 0. The last peice would fail. Still, thats not the problem now.

Anthony Mushrow11-Sep-07 14:52

Re: Opening large files / sockets [solved]

11-Sep-07 14:52

The progress bar. Set the value Maximum to the length of the file, and the Value of the bar to the current position. It was the quickest way for testing purposes, and now it comes back to haunt me.

I even checked how it would react with a console app, which revealed it would just be set to the maximum number for an int, if the file length was too long. But apparently, it makes the app stop, no cryptic error, nothing, it just stops.

Still, i'll just set the max to 100 and use a percentage. So glad i figured that out, i wouldn't have been able to sleep.
And tomorrow, lots of try and catch.

Thanks for the help.

Luc Pattyn11-Sep-07 16:15

Luc Pattyn

11-Sep-07 16:15

You never told us about a progress bar.
It works with int, not long; and it throws exceptions when it is unhappy...

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Re: Opening large files / sockets [solved]

Anthony Mushrow12-Sep-07 2:06

C# equivalent of getch ()

12-Sep-07 2:06

Yeah, i didn't think it would be a problem, since i tested it with a console app, and it seemed fine. Alas.
Of course, if it crashed at setting the length of the progress bar, how did it send the first part of the file OMG | :OMG:

It will forever be a mistery.

Jordanwb11-Sep-07 11:48

11-Sep-07 11:48

I'm porting a game I made for C++ into C# and I can't find an equivalent of getch(). I found the "Keys" object but it's not quite what I want (or maybe I'm not using it right). Basically what my game does is that it waits for the user to press a key (primarily the directional keys) and acts based on the key pressed.

[Edit]

I forgot to mention this isn't a console app it's a Windows App.

User 665811-Sep-07 12:14

User 6658

11-Sep-07 12:14

ReadKey from the .NET 2.0 framework should be what you are looking for. You can also test for Keys.Left, Keys.Right etc.

regards

modified 12-Sep-18 21:01pm.

Jordanwb11-Sep-07 12:23

11-Sep-07 12:23

I couldn't find any Readkey when I typed in "Read". I tried using Keys.Left and so on but that class doesn't wait until you pressed a key which I need it to do. Alls it does is if a key is pressed return it otherwise return "None" and continue on.

But Thanks.

Dave Doknjas11-Sep-07 14:08

Dave Doknjas

11-Sep-07 14:08

Console.ReadKey(true).KeyChar

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Jordanwb11-Sep-07 14:15

11-Sep-07 14:15

So that'll work even though I'm not using a console window? (Just making sure)

Dave Doknjas11-Sep-07 14:33

Dave Doknjas

11-Sep-07 14:33

You would have to use a console window in C# to do the equivalent of getch() in C++.

Jordanwb11-Sep-07 15:10

11-Sep-07 15:10

Yeah so my question is is there a way for the Windows App to wait until a key is pressed then return the key pressed?

Brady Kelly11-Sep-07 22:11

Brady Kelly

11-Sep-07 22:11

Just respond to a KeyPress even - the application is already waiting for all kinds of input, and it would love to tell you if only you would listen. Basically, set the KeyPreview property of your main form to True, and then response to the KeyDown even from that form.

private void Form1_KeyDown(object sender, KeyEventArgs e)
{
    if ((e.KeyCode == Keys.Left) || (e.KeyCode == Keys.Right))
        // Move left or right.
}

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Jordanwb12-Sep-07 8:33