Provided by: tcllib_1.17-dfsg-1_all 
NAME
transfer::transmitter - Data source
SYNOPSIS
package require Tcl 8.4
package require snit ?1.0?
package require transfer::copy ?0.2?
package require transfer::data::source ?0.2?
package require transfer::connect ?0.2?
package require transfer::transmitter ?0.2?
transfer::transmitter objectName ?options...?
transfer::transmitter stream channel chan host port ?arg...?
transfer::transmitter stream file path host port ?arg...?
objectName method ?arg arg ...?
objectName destroy
objectName start
objectName busy
_________________________________________________________________________________________________
DESCRIPTION
This package pulls data sources and connection setup together into a combined object for
the transmission of information over a socket. These objects understand all the options
from objects created by the packages transfer::data::source and transfer::connect.
API
PACKAGE COMMANDS
transfer::transmitter objectName ?options...?
This command creates a new transmitter 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.
The object command will be created under the current namespace if the objectName is
not fully qualified, and in the specified namespace otherwise. The fully qualified
name of the object command is returned as the result of the command.
transfer::transmitter stream channel chan host port ?arg...?
This method creates a fire-and-forget transfer for the data contained in the
channel chan, starting at the current seek location. The channel is configured to
use binary translation and encoding for the transfer. The channel is automatically
closed when the transfer has completed.
If both host and port are provided an active connection to the destination is made.
If only a port is specified (with host the empty string) then a passive connection
is made instead.
Any arguments after the port are treated as options and are used to configure the
internal transmitter object. See the section Options for a list of the supported
options and their meaning. Note however that the signature of the command prefix
specified for the -command callback differs from the signature for the same option
of the transmitter object. This callback is only given the number of bytes and
transfered, and possibly an error message. No reference to the internally used
transmitter object is made.
The result returned by the command is the empty string if it was set to make an
active connection, and the port the internal transmitter object is listening on
otherwise, i.e when it is configured to connect passively. See also the package
transfer::connect and the description of the method connect for where this
behaviour comes from.
transfer::transmitter stream file path host port ?arg...?
This method is like stream channel, except that the data contained in the file path
is transfered.
OBJECT COMMAND
All objects created by the ::transfer::transmitter 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. Doing so while a transmission is in progress will
cause errors later on, when the transmission completes and tries to access the now
missing data structures of the destroyed object.
objectName start
This method initiates the data transmission, setting up the connection first and
then copying the information. The method will throw an error if a transmission is
already/still in progress. I.e. it is not possible to run two transmissions in
parallel on a single object, only in sequence. Multiple transmitter objects are
needed to manage parallel transfers, one per transmission. Errors will also be
thrown if the configuration of the data source is invalid, or if no completion
callback was specified.
The result returned by the method is the empty string for an object configured to
make an active connection, and the port the object is listening on otherwise, i.e
when it is configured to connect passively. See also the package transfer::connect
and the description of the method connect for where this behaviour comes from.
objectName busy
This method returns a boolean value telling us whether a transmission is in
progress (True), or not (False).
OPTIONS
All transmitter objects support the union of the options supported by their connect and
data source components, plus two of their own. See also the documentation for the
packages transfer::data::source and transfer::connect.
-blocksize int
This option specifies the size of the chunks to be transmitted in one block. Usage
is optional, its default value is 1024.
-command cmdprefix
This option specifies the command to invoke when the transmission of the
information has been completed. The arguments given to this command are the same
as given to the completion callback of the command transfer::copy::do provided by
the package transfer::copy.
-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.
The envisioned main use is the specfication of tls::socket. I.e. this option
allows the creation of secure transfer channels, without making this package
explicitly dependent on the tls package.
See also section Secure connections.
-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).
-string text
This option specifies that the source of the data is an immediate string, and its
associated argument contains the string in question.
-channel handle
This option specifies that the source of the data is a channel, and its associated
argument is the handle of the channel containing the data.
-file path
This option specifies that the source of the data is a file, and its associated
argument is the path of the file containing the data.
-variable varname
This option specifies that the source of the data is a string stored in a variable,
and its associated argument contains the name of the variable in question. The
variable is assumed to be global or namespaced, anchored at the global namespace.
-size int
This option specifies the size of the data transfer. It is optional and defaults to
-1. This value, and any other value less than zero signals to transfer all the data
from the source.
-progress command
This option, if specified, defines a command to be invoked for each chunk of bytes
transmitted, allowing the user to monitor the progress of the transmission of the
data. The callback is always invoked with one additional argument, the number of
bytes transmitted so far.
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::transmitter T -socketcmd tls::socket ...
...
TLS SECURITY CONSIDERATIONS
This package uses the TLS package to handle the security for https urls and other socket
connections.
Policy decisions like the set of protocols to support and what ciphers to use are not the
responsibility of TLS, nor of this package itself however. Such decisions are the
responsibility of whichever application is using the package, and are likely influenced by
the set of servers the application will talk to as well.
For example, in light of the recent POODLE attack
[http://googleonlinesecurity.blogspot.co.uk/2014/10/this-poodle-bites-exploiting-
ssl-30.html] discovered by Google many servers will disable support for the SSLv3
protocol. To handle this change the applications using TLS must be patched, and not this
package, nor TLS itself. Such a patch may be as simple as generally activating tls1
support, as shown in the example below.
package require tls
tls::init -tls1 1 ;# forcibly activate support for the TLS1 protocol
... your own application code ...
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 Trackers
[http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for enhancements you
may have for either package and/or documentation.
KEYWORDS
channel, copy, data source, secure, ssl, tls, transfer, transmitter
CATEGORY
Transfer module
COPYRIGHT
Copyright (c) 2006-2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>