NAME

pop3d - Tcl POP3 server implementation

Table Of Contents

• Table Of Contents

• Synopsis

• Description

• Options

• Authentication

• Mailboxes

• Secure mail transfer

• References

• Bugs, Ideas, Feedback

• Keywords

• Category

• Copyright

SYNOPSIS

package require Tcl 8.3
package require pop3d ?1.1.0?

::pop3d::new ?serverName?
serverName option ?arg arg ...?
serverName up
serverName down
serverName destroy ?mode?
serverName configure
serverName configure -option
serverName configure -option value...
serverName cget -option
serverName conn list
serverName conn state id
authCmd exists name
authCmd lookup name
storageCmd dele mbox msgList
storageCmd lock mbox
storageCmd unlock mbox
storageCmd size mbox ?msgId?
storageCmd stat mbox
storageCmd get mbox msgId

DESCRIPTION

• ::pop3d::new ?serverName?

  This command creates a new server object with an associated global Tcl command whose name is serverName.

The command serverName may be used to invoke various operations on the server. It has the following general form:

• serverName option ?arg arg ...?

  Option and the args determine the exact behavior of the command.

A pop3 server can be started on any port the caller has permission for from the operating system. The default port will be 110, which is the port defined by the standard specified in RFC 1939 (http://www.rfc-editor.org/rfc/rfc1939.txt). After creating, configuring and starting a the server object will listen for and accept connections on that port and handle them according to the POP3 protocol.

Note: The server provided by this module will handle only the basic protocol by itself. For the higher levels of user authentication and handling of the actual mailbox contents callbacks will be invoked.

The following commands are possible for server objects:

• serverName up

  After this call the server will listen for connections on its configured port.

• serverName down

  After this call the server will stop listening for connections. This does not affect existing connections.

• serverName destroy ?mode?

  Destroys the server object. Currently open connections are handled depending on the chosen mode. The provided modes are:

  • kill

    Destroys the server immediately, and forcefully closes all currently open connections. This is the default mode.

  • defer

    Stops the server from accepting new connections and will actually destroy it only after the last of the currently open connections for the server is closed.

• serverName configure

  Returns a list containing all options and their current values in a format suitable for use by the command array set. The options themselves are described in section Options.

• serverName configure -option

  Returns the current value of the specified option. This is an alias for the method cget. The options themselves are described in section Options.

• serverName configure -option value...

  Sets the specified option to the provided value. The options themselves are described in section Options.

• serverName cget -option

  Returns the current value of the specified option. The options themselves are described in section Options.

• serverName conn list

  Returns a list containing the ids of all connections currently open.

• serverName conn state id

  Returns a list suitable for [array set] containing the state of the connection referenced by id.

Options

The following options are available to pop3 server objects.

• -port port

  Defines the port to listen on for new connections. Default is 110. This option is a bit special. If port is set to "0" the server, or rather the operating system, will select a free port on its own. When querying -port the id of this chosen port will be returned. Changing the port while the server is up will neither change the returned value, nor will it change on which port the server is listening on. Only after resetting the server via a call to down followed by a call to up will the new port take effect. It is at that time that the value returned when querying -port will change too.

• -auth command

  Defines a command prefix to call whenever the authentication of a user is required. If no such command is specified the server will reject all users. The interface which has to be provided by the command prefix is described in section Authentication.

• -storage command

  Defines a command prefix to call whenever the handling of mailbox contents is required. If no such command is specified the server will claim that all mailboxes are empty. The interface which has to be provided by the command prefix is described in section Mailboxes.

• -socket command

  Defines a command prefix to call for opening the listening socket. This can be used to make the pop3 server listen on a SSL socket as provided by the tls package, see the command tls::socket.

Authentication

Here we describe the interface which has to be provided by the authentication callback so that pop3 servers following the interface of this module are able to use it.

• authCmd exists name

  This method is given a username and has to return a boolean value telling whether or not the specified user exists.

• authCmd lookup name

  This method is given a username and has to return a two-element list containing the password for this user and a storage reference, in this order.

  The storage reference is passed unchanged to the storage callback, see sections Options and Mailboxes for either the option defining it and or the interface to provide, respectively.

Mailboxes

Here we describe the interface which has to be provided by the storage callback so that pop3 servers following the interface of this module are able to use it. The mbox argument is the storage reference as returned by the lookup method of the authentication command, see section Authentication.

• storageCmd dele mbox msgList

  Deletes the messages whose numeric ids are contained in the msgList from the mailbox specified via mbox.

• storageCmd lock mbox

  This method locks the specified mailbox for use by a single connection to the server. This is necessary to prevent havoc if several connections to the same mailbox are open. The complementary method is unlock. The command will return true if the lock could be set successfully or false if not.

• storageCmd unlock mbox

  This is the complementary method to lock, it revokes the lock on the specified mailbox.

• storageCmd size mbox ?msgId?

  Determines the size of the message specified through its id in msgId, in bytes, and returns this number. The command will return the size of the whole maildrop if no message id was specified.

• storageCmd stat mbox

  Determines the number of messages in the specified mailbox and returns this number.

• storageCmd get mbox msgId

  Returns a handle for the specified message. This handle is a mime token following the interface described in the documentation of package mime. The pop3 server will use the functionality of the mime token to send the mail to the requestor at the other end of a pop3 connection.

Secure mail transfer

The option -socket (see Options) enables users of the package to override how the server opens its listening socket. The envisioned main use is the specification of the tls::socket command, see package tls, to secure the communication.

package require tls
tls::init \
	...

pop3d::new S -socket tls::socket
...

References

1. RFC 1939

2. RFC 2449

Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category pop3d of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

KEYWORDS

internet, network, pop3, protocol, rfc 1939, secure, ssl, tls

CATEGORY

Networking

COPYRIGHT

Copyright © 2002-2009 Andreas Kupries
Copyright © 2005 Reinhard Max