SI File Transfer This specification defines a profile of the XMPP stream initiation extension for transferring files between two entities. The protocol provides a modular framework that enables the exchange of information about the file to be transferred as well as the negotiation of parameters such as the transport to be used. This XMPP Extension Protocol is copyright © 1999 – 2024 by the XMPP Standards Foundation (XSF). Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation. ## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ## In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages. This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA). 0096 Deprecated Standards Track Standards Council XMPP Core XEP-0095 XEP-0234 si-filetransfer http://www.xmpp.org/schemas/file-transfer.xsd Thomas Muldowney temas@jabber.org temas@jabber.org Matthew Miller linuxwolf@outer-planes.net linuxwolf@outer-planes.net Ryan Eatmon reatmon@jabber.org reatmon@jabber.org Peter Saint-Andre stpeter@stpeter.im stpeter@jabber.org https://stpeter.im/ 1.3.1 2022-03-22 gl Fix incorrect reference to sipub namespace 1.3 2017-11-29 XEP Editor (ssw) Deprecated by vote of the council. 1.2 2004-04-13 psa More fully defined the XMPP Registrar considerations. 1.1 2003-12-30 psa Improved explanatory text; fixed several errors in the schema. 1.0 2003-10-17 psa Per a vote of the Jabber Council, advanced status to Draft. 0.7 2003-10-07 tjm Added IBB as a MUST requirement. 0.6 2003-08-18 tjm Cleaned up some namespace inconsistencies, added the <desc> element for file descriptions. 0.5 2003-07-15 rwe Stream ids not needed on return results. Moved s5b, ibb, and url-data to the actual namespaces of the stream protocols. 0.4 2003-06-30 lw Fixed various typos and inconsistencies 0.3 2003-06-30 lw Added XML Schema 0.2 2003-06-24 tjm Clarified many examples, added linuxwolf as an author (again, my bad, should have been there), clarified the allowed streams and how data is sent over it. 0.1 2003-06-10 tjm Initial version.

The traditional mechanism for transferring files in the Jabber community is the Out-of-Band Data (XEP-0066) XEP-0066: Out of Band Data <https://xmpp.org/extensions/xep-0066.html>. protocol. That protocol has several drawbacks:

  1. It is not reliable.
  2. It does not work when one of the parties is behind a firewall.
  3. It provides limited metadata about files to be exchanged.

The current document defines a profile of Stream Initiation (XEP-0095) XEP-0095: Stream Initiation <https://xmpp.org/extensions/xep-0095.html>. that solves the problems with out-of-band data, thus providing a robust, reliable mechanism for file transfers over the Jabber network. Implementors are referred to XEP-0095 regarding the underlying concepts of stream initiation.

The file transfer profile is in the "http://jabber.org/protocol/si/profile/file-transfer" namespace. The profile is fairly simple: it consists of the root element with the possibility of one child describing the optional ranged transfers.

The root element is <file> and has four attributes. The attributes are used only during the offer stage of stream initiation:

The size and name attributes MUST be present in the profile. The other attributes MAY be present.

There are two possible child elements of the root: <desc> and <range>. Both are OPTIONAL.

<desc> is used to provide a sender-generated description of the file so the receiver can better understand what is being sent. It MUST NOT be sent in the result.

When <range> is sent in the offer, it should have no attributes. This signifies that the sender can do ranged transfers. When a Stream Initiation result is sent with the <range> element, it uses these attributes:

Both attributes are OPTIONAL on the <range> element. Sending no attributes is synonymous with not sending the <range> element. When no <range> element is sent in the Stream Initiation result, the Sender MUST send the complete file starting at offset 0. More generally, data is sent over the stream byte for byte starting at the offset position for the length specified.

In order to enable seamless file transfer and appropriate fall-back mechanisms, implementations of this profile MUST support both SOCKS5 Bytestreams (XEP-0065) XEP-0065: SOCKS5 Bytestreams <https://xmpp.org/extensions/xep-0065.html>. and In-Band Bytestreams (XEP-0047) XEP-0047: In-Band Bytestreams <https://xmpp.org/extensions/xep-0047.html>., to be preferred in that order. The associated namespaces are to be included as option values for the "stream-method" variable as shown in the examples below.

Additionally, implementations MAY support other mechanisms.

 ]]> http://jabber.org/protocol/bytestreams ]]> This is a test. If this were a real file... ]]> http://jabber.org/protocol/bytestreams ]]>

This range should retrieve 256 bytes from the beginning of the file:

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This range should retrieve 256 bytes starting from the 128th byte in the file:

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This range should retrieve the remainder of the file starting at the 128th byte in the file:

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This range is the same as having not sent the range request and the entire file is sent:

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No interaction with the Internet Assigned Numbers Authority (IANA) The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>. is required as a result of this document.

The profile described in this document is included in the stream initiation profiles registry maintained by the XMPP Registrar The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>. (see <https://xmpp.org/registrar/si-profiles.html>). The registry submission is as follows:

http://jabber.org/protocol/si/profile/file-transfer XEP-0096 A profile for file transfer between any two entities. ]]>

As authorized by XMPP URI Query Components (XEP-0147) XEP-0147: XMPP URI Query Components <https://xmpp.org/extensions/xep-0147.html>., the XMPP Registrar maintains a registry of queries and key-value pairs for use in XMPP URIs (see <https://xmpp.org/registrar/querytypes.html>).

As described below, the registered querytypes for file transfer actions are "sendfile" and "recvfile". Note well that "sendfile" means a second entity will send a file to the XMPP entity that controls the IRI/URI and that "recvfile" means a second entity will receive a file from the XMPP entity that controls the IRI/URI.

To enable a second entity to send a file, the IRI/URI is of the following form:

The application SHOULD then present an interface enabling the user to provide information about the file to be sent (e.g., by "browsing" the file system of the user's computer in order to choose a file). As a result, the application SHOULD then send a Publishing Stream Initiation Requests (XEP-0137) XEP-0137: Publishing Stream Initiation Requests <https://xmpp.org/extensions/xep-0137.html>. message to the XMPP address encapsulated in the IRI/URI:

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The following submission registers the "sendfile" querytype.

sendfile http://jabber.org/protocol/si/profile/file-transfer enables initiation of an inbound file transfer to XMPP entity XEP-0096 ]]>

To enable a second entity to receive a file, the IRI/URI is of the following form:

That IRI/URI is equivalent to the following XML stanza:

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In accordance with Publishing Stream Initiation Requests (XEP-0137) XEP-0137: Publishing Stream Initiation Requests <https://xmpp.org/extensions/xep-0137.html>., the application SHOULD then initiate a file transfer exchange with by sending a stanza of the following form:

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Note well that the request to begin the stream is sent to the full JID (user@host/resource) of the XMPP entity identified by the XMPP IRI/URI. Therefore, the IRI/URI SHOULD include a full JID. If it does not, the receiver MUST discover a full JID via presence or service discovery. If the receiver cannot discover a full JID for the sender (e.g., in the last resort through sending a presence subscription request to the sender and receiving presence from the sender's resources), then it SHOULD abort the file transfer exchange.

The following submission registers the "recvfile" querytype.

recvfile http://jabber.org/protocol/si/profile/file-transfer enables initiation of an outbound file transfer from XMPP entity XEP-0096 algo the hash algorithm used to generate the checksum hash a checksum of the file contents mime-type the MIME type of the file being offered name the name of the file being offered sid the session ID associated with the file being offered size the size in bytes of the file being offered ]]> The protocol documented by this schema is defined in XEP-0096: http://www.xmpp.org/extensions/xep-0096.html ]]>