Connection control

This application runs on a separate thread for each connected user. It is responsible for listening on the user socket on one hand and listening on the ICQ network on the other. The connection control function is implemented in the files:

• connector.h
• connector.c

In the connection control module we are introduced to the structure of ``link environment'' (struct link_env). This structure includes the ICQLINK of the connection (which is the session identifiers for the icqlib library as can be read in the icqlib manual submitted with this documentation) along with additional information about the connection. The link environment contains the following properties:

• The ICQLINK of the connection.
• An identifier to whether the contact list has been initialized.
• The user's contact list. The contact list is implemented as a linked list and will be described in detail when we talk about the database.
• An identifier to whether the link is active.
• A pointer that can point to any additional data.
• The socket of the connection to the client.
• An identifier to whether the session has ended or not. This is required for purposes of flow of control.

The main function of the connection control mechanism is connector(). This function is called when the thread is initiated and handles flow of control until the connection is closed.

The function first initializes the environment and then goes on a look that is active as long as the identifier in the environment is set to a true value.

In the loop, we check for information from the ICQ network and for information from the user.

• If the connection to the ICQ network has been established (there is an identifier for that in the environment), the function first checks whether it's time to send another keepalive message to the ICQ network. If so, it sends a keepalive message. Then it checks for new messages from the ICQ network using the icq_Main() function. This function calls the appropriate callbacks if necessary (please check the icqlib manual for more information on the structure of icqlib).

• The function then checks for new information on the client connection and if there's a new information on that, it extracts the message and handles it. Extracting the message is simply a matter of socket programming. Handling the message is also made simple by our protocol structure. All we have to do is read the message type and send the message to the appropriate handler (we will elaborate on the handlers later).

Before the connection control function returns, it cleans the environment, releasing all allocated resources.