Re: Why server doesn't respond? [modified] - C# Discussion Boards

7-Oct-09 7:46

I have made server with this code and in new form. When I push button that loads this form it stops.

private void server_Load(object sender, EventArgs e)
        {
            
            Int32 port = 1111;
            IPAddress localAddr = IPAddress.Parse("127.0.0.1");

            TcpListener tcpListener = new TcpListener(localAddr, port);
            
            tcpListener.Start();
            Console.WriteLine("Strežnik pognan...");
            

            try
            {
                
                    //Sprejemanje novih odjemalcev
                    Socket socketForClient = tcpListener.AcceptSocket();

                    while (true)
                    {
                        if (socketForClient.Connected)
                        {

                            MessageBox.Show("Odjemalec povezan " + socketForClient.RemoteEndPoint.ToString(), "Napaka", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                            NetworkStream networkStream = new NetworkStream(socketForClient);
                            StreamWriter streamWriter = new StreamWriter(networkStream);
                            StreamReader streamReader = new StreamReader(networkStream);
                            string line = streamReader.ReadLine();
                            textBox1.Text = "Sprejeto: " + line;
                            line = line.ToUpper();
                            streamWriter.WriteLine(line);
                            Console.WriteLine("Poslano: " + line);
                            streamWriter.Flush();
                            Console.WriteLine();
                        }
                        socketForClient.Close();
                    }
            }
            catch (Exception x)
            {
                Console.WriteLine(x.ToString());
            }

When i connect client(also new form) to it..client form opens(client connected) but server form still isn't responding. Now i would like to type something in client and this message would be also writen lets say in textbox in server. If i delete while(true) it works but only first time. What should i do that it would work multiple times.

Please help

Luc Pattyn7-Oct-09 9:05

Luc Pattyn

7-Oct-09 9:05

Hi,

IMO there are a few problems:

1.
Socket socketForClient = tcpListener.AcceptSocket(); is a blocking call, which means it returns only when the connection is established. So the thread will have to wait; as the code seems to be inside a Form's Load handler, that Form will not show nor function as long as you don't have a connection.

2.
the whole if (socketForClient.Connected)... statement sits inside a while loop which has no way to terminate, so your code will never finish the Load handler, your Form will never become alive.

The solution to both problems is to use a separate thread; that way your Form can start, and react to your operations, while the other thread deals with the networking. Handlers running on the GUI thread (such as a Load handler) should never take more than some 30 milliseconds, which basically means all networking should always be performed by some other thread.

Smile | :)

Luc Pattyn

I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages

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Aljaz1118-Oct-09 0:17

8-Oct-09 0:17

Ok i changed it somehow now..it works now.. now next step for me is to transfer data for drawing. Lets say i draw circle in client..how to send data(x,y,width,heigth,colour) of it to server, so circle would be also drawn there?

Thanks,
Bye

Re: Why server doesn't respond? [modified]

Luc Pattyn8-Oct-09 1:10

Luc Pattyn

8-Oct-09 1:10

So you need to define a "language" that you will use to communicate between both apps; it must cover all the functionality you plan to support. First decision is text versus binary; text is the preferred way for portability and ease of debugging; binary would be somewhat more compact and faster. Go for text!

example (just one from an infinite number of possibilities; each #x is a number):

color,#r,#g,#b;        // set color
circle,#x,#y,#w,#h;    // draw circle
end;

Luc Pattyn

I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages

Local announcement (Antwerp region): Lange Wapper? Neen!

Aljaz1118-Oct-09 5:31

8-Oct-09 5:31

For the first time i send string to server it works..second time it gives me this error:

<br />
A first chance exception of type 'System.InvalidOperationException' occurred in System.dll<br />
An unhandled exception of type 'System.InvalidOperationException' occurred in System.dll<br />
<br />
Additional information: The operation is not allowed on non-connected sockets.<br />
<br />
The thread 'vshost.RunParkingWindow' (0xf94) has exited with code 0 (0x0).<br />
The program '[6184] server_client.vshost.exe: Managed' has exited with code -532459699 (0xe0434f4d).<br />

I am getting something for sockets..but on server_load sockets starts and they don't stop. Do i have to make new socket for every new string i send? I am beginner here so plz don't judge me if i ask simple questions.

Thanks for any help

modified on Thursday, October 8, 2009 11:47 AM

Luc Pattyn8-Oct-09 5:49

Luc Pattyn

8-Oct-09 5:49

why would you open and close the connection and the streams all the time? can't you just set them up once and keep them open?
That would imply you turn some of those variables into class members of course.

Smile | :)

Luc Pattyn

I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages

Local announcement (Antwerp region): Lange Wapper? Neen!

Aljaz1118-Oct-09 5:55

Re: Help is needed (Urgent)

8-Oct-09 5:55

Here is my code for sending:

private void poslji()
        {

            novo = textbox();
            NetworkStream networkStream = odjemalec.GetStream(); //odjemalec if global variable
            StreamReader streamReader = new StreamReader(networkStream);
            StreamWriter streamWriter = new StreamWriter(networkStream);
            
            streamWriter.WriteLine(novo);
            Console.WriteLine("Pošiljam sporočilo...");
            streamWriter.Flush();
            string s = streamReader.ReadLine();


            textBox1.Text = s;

            Console.WriteLine("Prejemam sporočilo...");
            Console.WriteLine(s);

            streamReader.Close();
            streamWriter.Close();
            networkStream.Close();

                
                    
        }

And here is code for server in server_load form:

try
            {
                IPAddress ipAd = IPAddress.Parse("127.0.0.1");
                

               
                TcpListener myList = new TcpListener(ipAd, int.Parse("1111"));

              
                myList.Start();

                Socket socketForClient = myList.AcceptSocket();

                Console.WriteLine("Odjemalec povezan " + socketForClient.RemoteEndPoint.ToString());
                NetworkStream networkStream = new NetworkStream(socketForClient);
                StreamWriter streamWriter = new StreamWriter(networkStream);
                StreamReader streamReader = new StreamReader(networkStream);
                string line = streamReader.ReadLine();
                Console.WriteLine("Sprejeto: " + line);
                line = line.ToUpper();
                textBox1.Text = line;
                streamWriter.WriteLine(line);
                Console.WriteLine("Poslano: " + line);
                
                streamWriter.Flush();
                Console.WriteLine();
               
                //socketForClient.Close();
               // myList.Stop();

it sends first time..next time error that i pasted in post before.

Help is needed (Urgent)

jashimu7-Oct-09 7:40

jashimu

7-Oct-09 7:40

Hello everyone, It has been long time I am trying to solve or deal with two ro more version of Excel file. It works for one not for others. Really don't know how to Accommodate all the different excel version in one project.

My Application works only with 2007 version.(The application in c#)

Jashim

EliottA7-Oct-09 9:07

EliottA

7-Oct-09 9:07

You're using the office primary interop assemblies version 12, you must also use the PIA's for version 11 which is office 2003.

Check out the CodeProject forum Guidelines[^]
The original soapbox 1.0 is back![^]

What's special with message box?

teknolog1237-Oct-09 6:56

teknolog123

7-Oct-09 6:56

hi,
I have a mainform(singleton)and a sub class which does a time related job and needs to show a messagebox at the end of the job. That's where the problem is. The mbox is shown but as soon as I click to OK button on mbox, program gives an exception. I changed my code in different ways but same result.

thanks in advance

PIEBALDconsult7-Oct-09 7:27

Re: What's special with message box? [modified]

7-Oct-09 7:27

Dunno. What Exception? Have you run it in the debugger?

teknolog1237-Oct-09 7:37

teknolog123

7-Oct-09 7:37

yes I ran it in the Debugger and it says "Couldn't find the instance of the object" and goes to the line below in Program.cs file

static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(MainForm.Instance); //this is the line
}
Note: when I remove the code for showing messagebox, everything is okay

modified on Wednesday, October 7, 2009 1:52 PM

LimitedAtonement7-Oct-09 7:42

LimitedAtonement

7-Oct-09 7:42

Where is MainForm defined? Is it the encapsulating class? Is Instance a static field? Is Instance instantiated? Any of these could be a problem. If MainForm is the encapsulating class, and this is all the code, then I would say, you need to add
MainForm.Instance = new <typename>();
Good luck.

In Christ,
Aaron Laws

teknolog1237-Oct-09 8:09

teknolog123

7-Oct-09 8:09

as a newbee,I'll try to answer.
mainform isn't defined somewhere,I made mainform a static singleton and all other classes access mainform members through its instance by saying: MainForm.Instance.xxxxx

PIEBALDconsult7-Oct-09 7:42

Another method safer than StreamWriter and how can I save the file on another server (asp.net c sharp)

7-Oct-09 7:42

Set a breakpoint where you show the MessageBox and step from there.

aspkiddy7-Oct-09 6:32

aspkiddy

7-Oct-09 6:32

I have a form: when the user fills a form, the application takes this information and creates a data file (.csv) and put it (data file) on the server in a directory (name of this directory is [information]) where the web site is located.

using (System.IO.StreamWriter SW = new System.IO.StreamWriter(Server.MapPath("save/information/Data_" + strDate + ".csv")))

{
 SW.WriteLine(s.FirstName + ";" + s.LastName + ";" + s.Address1 + ";");
 SW.Close();
}

After, I changed the path for save the file, in a different server than the Web server

StreamWriter SW = new StreamWriter(@"\\111.222.1.00\c$\Inetpub\wwwroot\site_toto\ save\information\Data_" + strDate + ".csv");

It must disable the firewall on server so that it works. I can’t it.

So instead of filing the file with system Windows, I'd like to put with FTP protocole on another place, but I do not know how I can do.

I have a class! How can I integrate it?

Is that correct if I do like that ? : Confused | :confused:

using (FTP ftplib = new FTP(MapPath ("Data_" + strDate + ".csv")));

try 
{
    ftplib.Connect("ftp.toto.com", 
                   "tata", 
                   "pata");
    ftplib.ChangeDir("information/");
}
catch(Exception ex)
{    
    Console.WriteLine(s.FirstName + ";" + s.LastName + ";" + s.Address1 + ";");
}

try
{ 
    int perc =  0;
    

    ftplib.OpenDownload("Data_" + strDate + ".csv", true);
    while(ftplib.DoDownload() > 0) 
    { 
        perc = (int)((ftplib.BytesTotal * 100)  / ftplib.FileSize); 
        Console.Write("\rDownloading: {0}/{1} {2}%", 
          ftplib.BytesTotal, ftplib.FileSize, perc);
        Console.Out.Flush();
    }
    Console.WriteLine("");
}
catch(Exception ex) 
{ 
    Console.WriteLine("");
    Console.WriteLine(ex.Message);
}

What do you think of my integration code that you see above? is that this can work or I'm completely wrong Confused | :confused:

Code Readability Poll

LimitedAtonement7-Oct-09 5:57

LimitedAtonement

7-Oct-09 5:57

Dear Sirs,

I just came across some code and changed it. I'm implementing the java Gridbag layout manager to a panel in C#, and in the Insets.Equals(object) code, the following could be found:

if (obj instanceof Insets) {
	    Insets insets = (Insets)obj;
	    return ((top == insets.top) && (left == insets.left) &&
		    (bottom == insets.bottom) && (right == insets.right));
	}
return false;

So I sharpified it:

if (obj is Insets)
{
    Insets insets = obj as Insets;
    return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
}
return false;

Then, almost compulsively, I modified it thus:

Insets insets = obj as Insets;
if (ReferenceEquals(insets, null)) return false;
return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));

I do this kind of thing ALL the time. I would like some comments on readability and efficiency.

I guess to characterize the modification, I would say that I make it read more sequentially, without having to skip code (casting your eyes over code because in certain cases it would not be executed). Also, I'm crazy about conserving lines. I suppose that's because I'm not paid per line Wink | ;)

. I always use the same-line `if' if I can, and if not, I resort to the no-brace 'if'. Which sometimes means...oh yeah, let me show a line I wrote the other day. Here's what I first wrote:

foreach (Point a in _gr_pts)
{
    if (prev == Point.Empty || prev == a)
    {
        prev = a;
        continue;
    }
    g.DrawArc(_ap_pen, prev, a);
    prev = a;
}

Then, I changed it to:

foreach (Point a in _gr_pts)
{
    if (prev == Point.Empty || prev == a)
    {
        prev =a;
        continue;
    }
    //Crazy, I know.
    g.DrawLine(_ap_pen, prev, prev = a);
}

I tried for a while to figure out how to get the braces out of the if statement...oh yeah, I just realized that this is possible:
(I'm writing free-hand, so there may be typos...)

foreach (Point a in _gr_pts)
    if (prev == Point.Empty || prev == a)
    {
        prev = a;
        continue;
    }
    else g.DrawLine(_ap_pen, prev, prev = a);

I know some people swear by ALWAYS using braces in if, else, do, while, for, foreach statements, (and if I remember correctly, Visual studio has some option about including those compulsively) and I am a little curious if any of you are that way, or how many would do what I do.

To sum up, some items on which to comment:
I cast the object first without asking about the cast. I use ReferenceEquals, not `=='. I return false inline with the if-statement; I don't use else.

When I say things like `I don't use else,' I don't mean all the time, but I don't use it if I don't need it. Does anyone know if this affects effeciency in any way? I suppose I'm too lazy to check out the disassembly (because it's always SOO confusing Frown | :(

).

I look forward to hearing back from you, my esteemed colleagues.

In Christ,
Aaron Laws

Kevin Marois7-Oct-09 6:34

Kevin Marois

7-Oct-09 6:34

Aaron,

I teach C# at a local JC, and one thing I always stress is readability. White space and well defined blocks of
code are good because it allows your mind to process each item individually line by line, whereas this

Insets insets = obj as Insets;
if (ReferenceEquals(insets, null)) return false;
return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));

forces me to stop and pick apart these lines to digest all that is happening.

I find this to me much clearer

if (obj is Insets)
{    
	Insets insets = obj as Insets;    
	return ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
}
return false;

Also, one other thing we teach is having only one return in a method. It prevents "spaghetti code" where you
have to really hunt to see where the method is actually ending. So condider this:

bool bReturn = false;
if (obj is Insets)
{    
	Insets insets = obj as Insets;    
	bReturn = ((top == insets.top) && (left == insets.left) && (bottom == insets.bottom) && (right == insets.right));
}
return bReturn;

So now if I wanted to put more code in the method that I know will always run, all I have to do is find
the return & put the code above it.

Just my humble opinion.

Everything makes sense in someone's mind

N a v a n e e t h7-Oct-09 7:38

N a v a n e e t h

7-Oct-09 7:38

Kevin Marois wrote:
Also, one other thing we teach is having only one return in a method

IMO, this makes the code hard to read. Multiple return is the preferred approach. Martin Fowler has a topic on this in his Refactoring book. I don't have it right now to quote.

Smile | :)

Navaneeth

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PIEBALDconsult7-Oct-09 8:22

7-Oct-09 8:22

N a v a n e e t h wrote:
Martin Fowler

But is he the only one who says that? I prefer to make my own decisions rather than follow the word of one author.

Gideon Engelberth7-Oct-09 9:14

Gideon Engelberth

7-Oct-09 9:14

I've not read enough books (or this one by Fowler) to know if other people say it, but I would personally prefer to use multiple return points. The reality is that in some cases, such as when you have cleanup code that must run and a try-finally isn't appropriate, you may need to have only one return point. Other than that, there is little to no mental benefit to doing it either way. When I read this,

bool bReturn;
if (condition)
{    
    //do stuff
    bReturn = true;
}
else
{
    //do stuff
    if (other condition)
    {
        // yet more stuff
        bReturn = false;
    }
    else
    {
        //blah blah blah
        bReturn = true;
    }
}
return bReturn;

I still have to trace through the same amount of code to know what the function will return each case, whether I use single or multiple returns. Allowing multiple returns makes it obvious when some condition will stop execution of the method immediately. If I must have a single return, these conditions end up causing if-else statements that I have to trace to the end of the method before realizing that, "Hey, this condition stops the method." This will also usually end up leading to deeper nesting, which is more difficult to read.

PIEBALDconsult7-Oct-09 13:49