KalSMS SMS/MMS gateway for Android

Server API Reference

KalSMS communicates with the server via HTTP POST requests that expect an XML response.

For convenience, KalSMS includes server libraries and example code for certain languages to simplify handling its POST requests and generating response XML.

If a server library is not yet available for your programming language, you can still use KalSMS by implementing code in accordance with the API reference below. We encourage you to contribute new libraries and example code back to the KalSMS project!

HTTP Request Format

The following parameters are sent by all POST requests from KalSMS:

"version" ::= <integer>

The API version of the POST requests (currently "2").

This number will be incremented whenever the format of POST requests changes significantly. This allows the server to support phones running different API versions at the same time. If a deployment has many phones running with KalSMS, the server should update its code first, then the phones can be upgraded to the new version of KalSMS as convenient.

"phone_number" ::= <text>

The phone number of the phone running KalSMS, as entered under Menu > Settings.

This allows the server to differentiate between KalSMS clients if multiple phones are running KalSMS.

"action" ::= "outgoing" | "incoming" | "send_status"

The request action determines the purpose of the HTTP request:

"outgoing":: Poll the server for outgoing messages
"incoming":: Forward an incoming SMS or MMS message to the server
"send_status":: Update the server on the status of sending an outgoing message

The other POST parameters sent depend on the request action.

The following HTTP Headers are sent in all POST requests from KalSMS:

"X-Kalsms-Signature" ::= <text>

A signature of the request to verify the phone and the server share the same password (though it doesn't protect against MITM snooping or replay attacks).

The signature is calculated by the following algorithm:

Sort all POST parameters (not including file uploads) in alphabetical order by the name of the field.
Generate an input string by concatenating:
- the server URL,
- each of the sorted POST parameters with their corresponding values, and
- the password,
with a comma in between each element, like so:

"<serverURL>,<name1>,<value1>,<...>,<nameN>,<valueN>,<password>"
Generate the SHA-1 hash of the input string in UTF-8
Encode the SHA-1 hash using Base64 with no line breaks.

Additional parameters sent in POST requests with action=incoming:

"from" ::= <text>: The phone number of the message sender.
"message_type" ::= "sms" | "mms": Whether this message is an SMS or MMS.
"message" ::= <text>: The message body of the SMS, or the content of the text/plain part of the MMS.

Additional parameters sent in POST requests with action=incoming and message_type=mms:

"mms_parts" ::= <json_array>

Metadata for each part of the MMS. Each item in the JSON array is an object with the following keys and values:

"name" ::= <text>: The name of an additional form field where the content of the MMS part is sent as an attached file.
"cid" ::= <text>: The Content ID of the MMS part. This allows the server to resolve references in the SMIL part of the MMS (e.g. <img region="Image" src="cid:805"/>).
"type" ::= "application/smil" | "text/plain" | "image/jpeg" | ...: The Content Type of the MMS part.
"filename" ::= <text>: The filename of the MMS part, as sent by the sender phone, e.g. "Image001.jpg".

(Additional fields with the content of each MMS part. Text parts are encoded in UTF-8.)

Additional parameters sent in POST requests with action=outgoing:

(None)

Additional parameters sent in POST requests with action=send_status:

"id" ::= <text>: The Server's ID for the outgoing message (from the id attribute of an sms tag in a previous XML response from the server).
"status" ::= "queued" | "failed" | "sent": The current status of the outgoing message.
"error" ::= <text>: A description of the reason for the error, if the message failed to send; or, an empty string if the message has been sent successfully.

HTTP Response Format

For a successul request, the server should return HTTP status code 200. If the signature check failed, the server should return status code 403. Other status codes may be used to signify errors.

HTTP response format for action=incoming and action=outgoing:

The Content-Type header should be text/xml, with the content as follows:

<messages>

The root XML element.

Attributes:
none
Content:

<sms>*

The SMS messages to send.

<sms>

Describes an outgoing SMS to send.

Attributes:

"id" ::= <text> (optional)

An ID for this outgoing message. (KalSMS will send this back to the server as the id field in a send_status request.)

"to" ::= <text> (optional for incoming, required for outgoing)

The phone number to send the SMS to. If omitted for action=incoming, it will be sent as a reply to the original sender.

Content:

CDATA

The content of the SMS message to send.

Example:
    <?xml version='1.0' encoding='UTF-8'?>
    <messages>
        <sms id='42' to='5551212'>Message One</sms>
        <sms>Message Two</sms>
    </message>

Response format for action=send_status:

The response content is currently undefined and ignored.