Provided by: tcllib_1.19-dfsg-2_all bug

NAME

       transfer::receiver - Data source

SYNOPSIS

       package require Tcl  8.4

       package require snit  ?1.0?

       package require transfer::data::destination  ?0.2?

       package require transfer::connect  ?0.2?

       package require transfer::receiver  ?0.2?

       transfer::receiver object ?options...?

       transfer::receiver stream channel chan host port ?arg...?

       transfer::receiver stream file path host port ?arg...?

       objectName method ?arg arg ...?

       objectName destroy

       objectName start

       objectName busy

_________________________________________________________________________________________________

DESCRIPTION

       This  package pulls data destinations and connection setup together into a combined object
       for the reception of information coming in over a socket.  These  objects  understand  all
       the   options  from  objects  created  by  the  packages  transfer::data::destination  and
       transfer::connect.

API

   PACKAGE COMMANDS
       transfer::receiver object ?options...?
              This command creates a new receiver 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::receiver stream channel chan host port ?arg...?
              This  method creates a fire-and-forget transfer for the data coming from the source
              at host/port (details below) and writing to  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  not  closed  when  the  transfer  has
              completed. This is left to the completion callback.

              If both host and port are provided an active connection to the data source is made.
              If only a port is specified (with host the empty string) then a passive  connection
              is made instead, i.e. the receiver then waits for a conneciton by the transmitter.

              Any  arguments  after the port are treated as options and are used to configure the
              internal receiver 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  receiver  object.   This  callback  is  only given the number of bytes and
              transfered, and possibly an error message. No  reference  to  the  internally  used
              receiver 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  receiver  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::receiver stream file path host port ?arg...?
              This method is like stream channel, except that the received data is written to the
              file path, replacing any prior content.

   OBJECT COMMAND
       All objects created by the ::transfer::receiver 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 reception is on progress will
              cause errors later on, when the reception completes and tries  to  access  the  now
              missing data structures of the destroyed object.

       objectName start
              This  method initiates the data reception, setting up the connection first and then
              copying the received information into the destination.  The method  will  throw  an
              error  if a reception is already/still in progress.  I.e. it is not possible to run
              two receptions in parallel, only in sequence.  Errors will also be  thrown  if  the
              configuration  of the data destination 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 reception is in progress
              (True), or not (False).

   OPTIONS
       All receiver objects support the union of the options supported by their connect and  data
       destination  components,  plus  one  of  their  own.   See  also the documentation for the
       packages transfer::data::destination and transfer::connect.

       -command cmdprefix
              This option specifies the command to invoke when the reception 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).

       -channel handle
              This option specifies that the destination of  the  data  is  a  channel,  and  its
              associated argument is the handle of the channel to write the received data to.

       -file path
              This  option  specifies  that  the  destination  of  the  data  is  a file, and its
              associated argument is the path of the file to write the received data to.

       -variable varname
              This option specifies that the destination of the  data  is  a  variable,  and  its
              associated  argument  contains  the name of the variable to write the received data
              to. The variable is assumed to be global or  namespaced,  anchored  at  the  global
              namespace.

       -progress command
              This  option, if specified, defines a command to be invoked for each chunk of bytes
              received, allowing the user to monitor the progress of the reception of  the  data.
              The  callback  is  always invoked with one additional argument, the number of bytes
              received 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::receiver R -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.

       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

       channel, copy, data destination, receiver, secure, ssl, tls, transfer

CATEGORY

       Transfer module

COPYRIGHT

       Copyright (c) 2006 Andreas Kupries <andreas_kupries@users.sourceforge.net>