1transfer::receiver(n) Data transfer facilities transfer::receiver(n)
2______________________________________________________________________________
6
8 transfer::receiver - Data source
9
11 package require Tcl 8.4
12 package require snit ?1.0?
14 package require transfer::data::destination ?0.2?
16 package require transfer::connect ?0.2?
18 package require transfer::receiver ?0.2?
20 transfer::receiver object ?options...?
22 transfer::receiver stream channel chan host port ?arg...?
24 transfer::receiver stream file path host port ?arg...?
26 objectName method ?arg arg ...?
28 objectName destroy
30 objectName start
32 objectName busy
34______________________________________________________________________________
36
38 This package pulls data destinations and connection setup together into
39 a combined object for the reception of information coming in over a
40 socket. These objects understand all the options from objects created
41 by the packages transfer::data::destination and transfer::connect.
42
44 PACKAGE COMMANDS
45 transfer::receiver object ?options...?
46 This command creates a new receiver object with an associated
47 Tcl command whose name is objectName. This object command is
48 explained in full detail in the sections Object command and
49 Object methods. The set of supported options is explained in
50 section Options.
51 The object command will be created under the current namespace
53 if the objectName is not fully qualified, and in the specified
54 namespace otherwise. The fully qualified name of the object
55 command is returned as the result of the command.
56 transfer::receiver stream channel chan host port ?arg...?
58 This method creates a fire-and-forget transfer for the data com‐
59 ing from the source at host/port (details below) and writing to
60 the channel chan, starting at the current seek location. The
61 channel is configured to use binary translation and encoding for
62 the transfer. The channel is not closed when the transfer has
63 completed. This is left to the completion callback.
64 If both host and port are provided an active connection to the
66 data source is made. If only a port is specified (with host the
67 empty string) then a passive connection is made instead, i.e.
68 the receiver then waits for a conneciton by the transmitter.
69 Any arguments after the port are treated as options and are used
71 to configure the internal receiver object. See the section
72 Options for a list of the supported options and their meaning.
73 Note however that the signature of the command prefix specified
74 for the -command callback differs from the signature for the
75 same option of the receiver object. This callback is only given
76 the number of bytes and transfered, and possibly an error mes‐
77 sage. No reference to the internally used receiver object is
78 made.
79 The result returned by the command is the empty string if it was
81 set to make an active connection, and the port the internal
82 receiver object is listening on otherwise, i.e when it is con‐
83 figured to connect passively. See also the package trans‐
84 fer::connect and the description of the method connect for where
85 this behaviour comes from.
86 transfer::receiver stream file path host port ?arg...?
88 This method is like stream channel, except that the received
89 data is written to the file path, replacing any prior content.
90 OBJECT COMMAND
92 All objects created by the ::transfer::receiver command have the fol‐
93 lowing general form:
94 objectName method ?arg arg ...?
96 The method method and its arg'uments determine the exact behav‐
97 ior of the command. See section Object methods for the detailed
98 specifications.
99 OBJECT METHODS
101 objectName destroy
102 This method destroys the object. Doing so while a reception is
103 on progress will cause errors later on, when the reception com‐
104 pletes and tries to access the now missing data structures of
105 the destroyed object.
106 objectName start
108 This method initiates the data reception, setting up the connec‐
109 tion first and then copying the received information into the
110 destination. The method will throw an error if a reception is
111 already/still in progress. I.e. it is not possible to run two
112 receptions in parallel, only in sequence. Errors will also be
113 thrown if the configuration of the data destination is invalid,
114 or if no completion callback was specified.
115 The result returned by the method is the empty string for an
117 object configured to make an active connection, and the port the
118 object is listening on otherwise, i.e when it is configured to
119 connect passively. See also the package transfer::connect and
120 the description of the method connect for where this behaviour
121 comes from.
122 objectName busy
124 This method returns a boolean value telling us whether a recep‐
125 tion is in progress (True), or not (False).
126 OPTIONS
128 All receiver objects support the union of the options supported by
129 their connect and data destination components, plus one of their own.
130 See also the documentation for the packages transfer::data::destination
131 and transfer::connect.
132 -command cmdprefix
134 This option specifies the command to invoke when the reception
135 of the information has been completed. The arguments given to
136 this command are the same as given to the completion callback of
137 the command transfer::copy::do provided by the package trans‐
138 fer::copy.
139 -mode mode
141 This option specifies the mode the object is in. It is optional
142 and defaults to active mode. The two possible modes are:
143 active In this mode the two options -host and -port are relevant
145 and specify the host and TCP port the object has to con‐
146 nect to. The host is given by either name or IP address.
147 passive
149 In this mode the option -host has no relevance and is
150 ignored should it be configured. The only option the
151 object needs is -port, and it specifies the TCP port on
152 which the listening socket is opened to await the connec‐
153 tion from the partner.
154 -host hostname-or-ipaddr
156 This option specifies the host to connect to in active mode,
157 either by name or ip-address. An object configured for passive
158 mode ignores this option.
159 -port int
161 For active mode this option specifies the port the object is
162 expected to connect to. For passive mode however it is the port
163 where the object creates the listening socket waiting for a con‐
164 nection. It defaults to 0, which allows the OS to choose the
165 actual port to listen on.
166 -socketcmd command
168 This option allows the user to specify which command to use to
169 open a socket. The default is to use the builtin ::socket. Any
170 compatible with that command is allowed.
171 The envisioned main use is the specfication of tls::socket. I.e.
173 this option allows the creation of secure transfer channels,
174 without making this package explicitly dependent on the tls
175 package.
176 See also section Secure connections.
178 -encoding encodingname
180 -eofchar eofspec
182 -translation transspec
184 These options are the same as are recognized by the builtin com‐
185 mand fconfigure. They provide the configuration to be set for
186 the channel between the two partners after it has been estab‐
187 lished, but before the callback is invoked (See method connect).
188 -channel handle
190 This option specifies that the destination of the data is a
191 channel, and its associated argument is the handle of the chan‐
192 nel to write the received data to.
193 -file path
195 This option specifies that the destination of the data is a
196 file, and its associated argument is the path of the file to
197 write the received data to.
198 -variable varname
200 This option specifies that the destination of the data is a
201 variable, and its associated argument contains the name of the
202 variable to write the received data to. The variable is assumed
203 to be global or namespaced, anchored at the global namespace.
204 -progress command
206 This option, if specified, defines a command to be invoked for
207 each chunk of bytes received, allowing the user to monitor the
208 progress of the reception of the data. The callback is always
209 invoked with one additional argument, the number of bytes
210 received so far.
211
213 One way to secure connections made by objects of this package is to
214 require the package tls and then configure the option -socketcmd to
215 force the use of command tls::socket to open the socket.
216 # Load and initialize tls
219 package require tls
220 tls::init -cafile /path/to/ca/cert -keyfile ...
221 # Create a connector with secure socket setup,
223 transfer::receiver R -socketcmd tls::socket ...
224 ...
225
228 This package uses the TLS package to handle the security for https urls
229 and other socket connections.
230 Policy decisions like the set of protocols to support and what ciphers
232 to use are not the responsibility of TLS, nor of this package itself
233 however. Such decisions are the responsibility of whichever applica‐
234 tion is using the package, and are likely influenced by the set of
235 servers the application will talk to as well.
236 For example, in light of the recent POODLE attack [http://googleonli‐
238 nesecurity.blogspot.co.uk/2014/10/this-poodle-bites-exploiting-
239 ssl-30.html] discovered by Google many servers will disable support for
240 the SSLv3 protocol. To handle this change the applications using TLS
241 must be patched, and not this package, nor TLS itself. Such a patch
242 may be as simple as generally activating tls1 support, as shown in the
243 example below.
244 package require tls
247 tls::init -tls1 1 ;# forcibly activate support for the TLS1 protocol
248 ... your own application code ...
250
253 This document, and the package it describes, will undoubtedly contain
254 bugs and other problems. Please report such in the category transfer
255 of the Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist]. Please
256 also report any ideas for enhancements you may have for either package
257 and/or documentation.
258 When proposing code changes, please provide unified diffs, i.e the out‐
260 put of diff -u.
261 Note further that attachments are strongly preferred over inlined
263 patches. Attachments can be made by going to the Edit form of the
264 ticket immediately after its creation, and then using the left-most
265 button in the secondary navigation bar.
266
268 channel, copy, data destination, receiver, secure, ssl, tls, transfer
269
271 Transfer module
272
274 Copyright (c) 2006 Andreas Kupries <andreas_kupries@users.sourceforge.net>
275tcllib 0.2 transfer::receiver(n)