2-Way
SMS Returning a Non-Text Response
Document ID:
TB-NOWSMS-003, Last Update: February 7, 2003
It is a relatively
simple process to define a 2-way command that
returns a text response to the message sender.
The “2-Way” page of the NowSMS configuration
dialog allows you to define commands that are
executed when an SMS message is received. The
receipt of an inbound SMS message by the gateway
can cause an executable command to be executed,
or the gateway can connect to an HTTP URL to run
a script on a separate web server. If “Command
returns response text” is set for the command,
it is simple for the command to return a text
response back to the sender of the SMS. In the
case of an HTTP URL, the HTTP URL can return a
simple text response with a MIME type for the
response set as “text/plain”, and
the gateway will automatically send this text
as a response back to the sender of the SMS.
In the example shown
in the screen shot above, the receipt of a text
SMS message causes the gateway to connect to
the HTTP URL:
http://192.168.1.102/cgi-bin/sms.cgi?Sender=@@Sender@@&Text=@@FullSMS@@
When a message is processed,
the “@@Sender@@” value is replaced
with the phone number of the sender of the received
message, and @@FullSMS@@ contains the complete
text of the received message.
What if an HTTP script
wants to return a response back to the sender
that is a non-text SMS format, such as WAP OTA
settings, a Nokia smart messaging message, or
even an MMS message?
The HTTP script could always
include its own processing logic to spawn a
command that issues a request back to the NowSMS
gateway, but this can be difficult. An alternative
approach is for the HTTP response to return
a “redirect” response, where the
redirect URL is a URL pointer back to the NowSMS
gateway, for example http://127.0.0.1:8800/?PhoneNumber=%2b12125551212&...
(If you want to be able to test your HTTP script
by executing it from a web browser, you will
need to substitute the real IP address of your
NowSMS server for the 127.0.0.1 address.)
If your NowSMS server requires
authentication, a username and password can
be included in the redirect response using the
URL format http://user:password@server.name/path.
Any URL that would work
when sent directly to the NowSMS server can
be returned as a “redirect” response.
If a script will be returning a “redirect”
response, it is important that “Command
returns response text” is NOT checked
for the command on the “2-Way” configuration
dialog. This is because a redirect response
simply instructs the HTTP client to retrieve
a different URL. The NowSMS gateway will not
return the actual response from that URL request
to the client.
An HTTP redirect response
is an HTTP 302 response, with the redirect URL
included in the “Location:” header,
for example:
HTTP/1.0 302 Redirect
Location: http://127.0.0.1:8800/?PhoneNumber=...
<blank line>
Most scripting languages
have built-in support for returning a redirect
response. For example, in an ASP script, Response.Redirect
(“http://127.0.0.1:8800/?PhoneNumber=...)
is used to send a redirect response. Other scripting
languages have similar support.
Return
to Now SMS/MMS Gateway Technical Bulletins
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