FTP Daemon

When an FTP client initiates a connection request, the FTP Daemon accepts and opens a Control Connection, and then spawns a thread group which acts as the FTP Protocol Engine and processes further requests from the client. A data connection is established between the Protocol Engine and the FTP client whenever required for file transfer.

When the FTPServer.NLM is loaded, the FTP daemon is started. The FTP daemon initializes the Configuration Parameters, Access Restrictions, Catalog services, Logs and statistics. The FTP Daemon binds to the FTP port specified in the configuration file and listens for connection requests from the clients.

On executing load ftpserv command, the FTP daemon is executed as the main thread. The FTP server can be unloaded at any time on executing the unload ftpserv command. While coming up, FTP Server initializes the following operations:

• Registers CleanupAndExitFTPServ() as function to be called while it is being unloaded
• Initializes UnloadFTPServ to zero
• Calls InitGlobalConfig() to initialize the configuration parameters global to FTP Server.
• Calls InitGlobalInfoAccess() to initialize the global data access locks.
• Gets the context of the FTP Server and stores in FTPContext.
• Initializes all functions related to Catalog Services for contextless login by calling InitializeCatalogFunctions()
• Imports all functions related to NetWare SAA for IBM-AFTP Support by calling ImportAFTPFunctions()
• Builds the user/host restrictions database by calling ReadAndBuildRestrictList()
• Initializes Intruder login detection by calling InitIntruderDetect()
• Initiates all logging by calling InitAllLogs()
• Initializes the facility of displaying the welcome banner / message file by calling InitWelcomeFile() and InitMsgFile()

After initialization, the FTP Daemon binds to the standard FTP port (21) or the port specified in the configuration file and listens for connection requests from FTP clients. On receiving a connection request, it establishes the Control Connection with the FTP client. It, then spawns a new thread in a separate thread group and hands over the socket information to Protocol Engine (ProtocolEngine) for processing the FTP commands that it receives on the connection.