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transfer::connect(3tcl) | Data transfer facilities | transfer::connect(3tcl) |
NAME¶
transfer::connect - Connection setupSYNOPSIS¶
package require Tcl 8.4DESCRIPTION¶
This package provides objects holding enough information to enable them to either actively connect to a counterpart, or to passively wait for a connection from said counterpart. I.e. any object created by this packages is always in one of two complementary modes, called active (the object initiates the connection) and passive (the object receives the connection). Of the two objects in a connecting pair one has to be configured for active mode, and the other then has to be configured for passive mode. This establishes which of the two partners connects to whom (the active to the other), or, who is waiting on whom (the passive on the other). Note that this is completely independent of the direction of any data transmission using the connection after it has been established. An active object can, after establishing the connection, either transmit or receive data. Equivalently the passive object can do the same after the waiting for its partner has ended.API¶
PACKAGE COMMANDS¶
- transfer::connect objectName ?options...?
- This command creates a new connection object with an
associated Tcl command whose name is objectName. This object
command is explained in full detail in the sections Object command
and Object methods. The set of supported options is
explained in section Options.
OBJECT COMMAND¶
All objects created by the ::transfer::connect command have the following general form:- objectName method ?arg arg ...?
- The method method and its arg'uments determine the exact behavior of the command. See section Object methods for the detailed specifications.
OBJECT METHODS¶
- objectName destroy
- This method destroys the object. This is safe to do for an active object when a connection has been started, as the completion callback is synchronous. For a passive object currently waiting for its partner to establish the connection however this is not safe and will cause errors later on, when the connection setup completes and tries to access the now missing data structures of the destroyed object.
- objectName connect command
- This method starts the connection setup per the
configuration of the object. When the connection is established the
callback command will be invoked with one additional argument, the
channel handle of the socket over which data can be transfered.
- active
- The connection setup is done synchronously. The object waits until the connection is established. The method returns the empty string as its result.
- passive
- The connection setup is done asynchronously. The method
returns immediately after a listening socket has been set up. The
connection will be established in the background. The method returns the
port number of the listening socket, for use by the caller. One important
use is the transfer of this information to the counterpart so that it
knows where it has to connect to.
OPTIONS¶
Connection objects support the set of options listed below.- -mode mode
- This option specifies the mode the object is in. It is optional and defaults to active mode. The two possible modes are:
- active
- In this mode the two options -host and -port are relevant and specify the host and TCP port the object has to connect to. The host is given by either name or IP address.
- passive
- In this mode the option -host has no relevance and is ignored should it be configured. The only option the object needs is -port, and it specifies the TCP port on which the listening socket is opened to await the connection from the partner.
- -host hostname-or-ipaddr
- This option specifies the host to connect to in active mode, either by name or ip-address. An object configured for passive mode ignores this option.
- -port int
- For active mode this option specifies the port the object is expected to connect to. For passive mode however it is the port where the object creates the listening socket waiting for a connection. It defaults to 0, which allows the OS to choose the actual port to listen on.
- -socketcmd command
- This option allows the user to specify which command to use
to open a socket. The default is to use the builtin ::socket. Any
compatible with that command is allowed.
- -encoding encodingname
- -eofchar eofspec
- -translation transspec
- These options are the same as are recognized by the builtin command fconfigure. They provide the configuration to be set for the channel between the two partners after it has been established, but before the callback is invoked (See method connect).
SECURE CONNECTIONS¶
One way to secure connections made by objects of this package is to require the package tls and then configure the option -socketcmd to force the use of command tls::socket to open the socket.# Load and initialize tls package require tls tls::init -cafile /path/to/ca/cert -keyfile ... # Create a connector with secure socket setup, transfer::connect C -socketcmd tls::socket ... ...
BUGS, IDEAS, FEEDBACK¶
This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category transfer of the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883]. Please also report any ideas for enhancements you may have for either package and/or documentation.KEYWORDS¶
active, channel, connection, passive, secure, ssl, tls, transferCATEGORY¶
Transfer moduleCOPYRIGHT¶
Copyright (c) 2006-2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>
0.2 | transfer |