Indy TCP Server exceptions

[gbrandt]

FIXED: see second entry


Hi,

I am asking alot of question lately Soon I hope to help answer some as well.

Windows 7, Builder 2010, standard install

I have the following code:

Code: Select all

      try
      {
         mTCPServer = new TIdTCPServer( NULL );
         mTCPServer->OnExecute =  MyExecute;
         mTCPServer->DefaultPort = 32790;
         mTCPServer->Active = true;
      }
      catch( ... )
      {
      }


in my constructor.

When I run this code I get two exceptions when I turn the server active:

Code: Select all

First chance exception at $75FE9617. Exception class EIdSocketError with message
'Socket Error # 10048
Address already in use.'.
Process PhaseManager.exe (3104)


and then

Code: Select all

First chance exception at $75FE9617. Exception class EIdCouldNotBindSocket with message 'Could not bind socket. Address and port are already in use.'. Process PhaseManager.exe (3104)


But the code works perfectly. I can telnet into 32790 and get a response (my OnExecute simply echos what I type with a timestamp).

I really should not be getting these exceptions because the open and bind appear to be working perfectly. Any ideas?

I do not get these exceptions if I drop a TcpServer on my unit, only if I 'new' it.

Thanks,
Gregor

[gbrandt]

[quote="gbrandt"]

Code: Select all

      try
      {
         mTCPServer = new TIdTCPServer( NULL );
         mTCPServer->OnExecute =  MyExecute;
         mTCPServer->DefaultPort = 32790;
         mTCPServer->Active = true;
      }
      catch( ... )
      {
      }


fixed by changing above code into:

Code: Select all

      try
      {
         mTCPServer = new TIdTCPServer( this );
         mTCPServer->OnExecute =  MyExecute;
         mTCPServer->DefaultPort = 32790;
         mTCPServer->Active = true;
      }
      catch( ... )
      {
      }


If I used owner instead of this, I would get my component as well as the TIDTCPServer component on my unit...wierd.

Gregor

[gambit47]

fixed by changing above code into:

Changing the assigned Owner of the TIdTCPServer component has no effect whatsoever on how it manages its sockets. Something else is happening.

[gambit47]

When I run this code I get two exceptions when I turn the server active

That error means that another process is already using port 32790 at the time when you activate your server.

But the code works perfectly.

That is not possible. If a bind failure occurs when activating the server, the listening sockets are shut down, the server is deactivated, and the exception is raised into your code.

I can telnet into 32790 and get a response (my OnExecute simply echos what I type with a timestamp).

Check if you have multiple instances of your app running at the same time.

I do not get these exceptions if I drop a TcpServer on my unit, only if I 'new' it.

How the TIdTCPServer object is created makes no difference whatsoever on how its sockets are managed.

[gbrandt]

That error means that another process is already using port 32790 at the time when you activate your server.

Nothing else was using the port, I even chose other random port numbers to verify.

But the code works perfectly.

That is not possible. If a bind failure occurs when activating the server, the listening sockets are shut down, the server is deactivated, and the exception is raised into your code.

I know its not possible, but it did happen. Could my constructor have been called twice? I placed the code in the constructor of the component. Does VCL do something weird here? And again, it ONLY happened when the argument was NULL, not when the argument was the parent Component.

Check if you have multiple instances of your app running at the same time.

Nope, only one instance.

Follow-up: thinking that my constructor could be called twice I checked and found ValidCtrCheck allocating an instance of my class and not deleting it. The pointer is not used anywhere, its not passed out of the function. So I added a delete to the function but that did not correct anything.

Gregor

[gambit47]

Nothing else was using the port, I even chose other random port numbers to verify.

Well, the error message (which came from the OS, BTW) stated otherwise. It said the port was in use.

I know its not possible, but it did happen. Could my constructor have been called twice?

That would only happen if you left the design-time component in your app, as well as the dynamically-created one in your code. But even if that happened, that would not typically cause the error since you are only activating 1 server object in your code. Unless you are activating the dynamic object in your code, and your design-time object was set to the same port and had Active=True in the Object Inspector. That would be the only way I could see both objects being active at the same time.

Follow-up: thinking that my constructor could be called twice I checked and found ValidCtrCheck allocating an instance of my class and not deleting it.

ValidCtrCheck() is not actually called by anything. It serves only as a compile-time checker to make sure your component class does not contain any abstract methods that have not been overwritten yet. A TObject-based class cannot be allocated on the stack, so ValidCtrCheck() has to use the 'new' operator, but since it is not actually being called, nothing is being allocated at run-time.

[gbrandt]

It turns out I was allocating and making active the server in my constructor. I wrapped that with a check to see if I was in designing mode and all is well.