[Live-devel] Removing sessions from RTSP Server

[Greg Bothe]

I ran into a small difficulty when managing a RTSP server.  For my
application, sessions come and go dynamically; the RTSP server does not send
out a constant set of audio streams.  The RTSPServer class has a
addServerMediaSession() method but no corresponding removeServerMediaSession()
method.  I suppose on most applications this isn't a problem, as all media
sessions will get removed when RTSPServer destructs.  However, for
applications such as mine, I need to tear down sessions throughout the
lifetime of the application.  I may be going about this wrong, but I believe I
have solved my problem by adding the following method to RTSPServer:

Boolean RTSPServer
::removeServerMediaSession(ServerMediaSession* serverMediaSession) {
  char const* sessionName = serverMediaSession->streamName();
  if (sessionName == NULL) sessionName = "";
  ServerMediaSession* existingSession
    = (ServerMediaSession*)
    (fServerMediaSessions->Lookup(sessionName));
  if(existingSession != NULL) {
    // Session is found, so remove it
    fServerMediaSessions->Remove(sessionName);
    delete existingSession;
    return True;
  }
  else {
    return False;
  }
}

In doing this change, I also believe I found a bug.  In HashTable.cpp, I had
to change the RemoveNext method from:

void* HashTable::RemoveNext() {
  Iterator* iter = Iterator::create(*this);
  char const* key;
  void* removedValue = iter->next(key);
  Remove(key);

  return removedValue;
}

to

void* HashTable::RemoveNext() {
  Iterator* iter = Iterator::create(*this);
  char const* key;
  void* removedValue = iter->next(key);
  if (removedValue != 0) {
    Remove(key);
  }

  return removedValue;
}

The code doesn't check to see if the next key actually exists before it tries
to remove the key.  Thus, Remove() gets passed a random memory address
(because key isn't initialized to NULL) and the program crashes.

I've been using the LiveMedia code now for a couple months.  It's been a GREAT
help.  For the record, I have the LiveMedia code compiled on Windows as a DLL
under Visual Studio 2003 so that I can dynamically link to it.  This took a
little bit of doing and it would be WONDERFUL if the standard LiveMedia
distribution supported DLL creation.  (If it does already, then I must have
way missed something.)  I wish I was developing under UNIX, but unfortunately,
I'm stuck on Windows for this project.

Greg Bothe