How the Bulk SMS Gateways are Made?

Just curious to know how such a system is built? Is Asterisk capable of making such a system. Currently having a requirement to just send SMS Messages from my custom made software. Decided not to go with the vendors. Possible by a single person’s effort? If not the entire gateway atleas simple system to just send and receive messages. If Message reception (incoming Message) is not possible. Atleast possible to send a same SMS to a group of 4 people?

Building a software for a Cab Hiring Agency. Whenever a booking is made. Need the following Messages to be sent (Only in SMS format. No other formats like WhatsApp/Skype/Teams)

  1. Customer information and Pickup Location Details to the Driver.
  2. Driver Contact Number and Vehicle Details like Cab Color, Number and Type.
  3. Vehicle Number and Opening KM Details for the Manager.
  4. Customer, Vehicle and Journey Details to the Owner.


With Hope,

Bulk gateways don’t use the air interface on the originate side, but would take the requests over the internet, not using VoIP protocols.

Can this be done with by Asterisk? Possibly, but for an SMS Gateway, Asterisk is the wrong tool.

TL;DR: Jump to last paragraph, at the bottom.

On linux you have smsd (At least with Debian it’s in the repo), which you can use for your purpose.

However, for HIGH volume traffic, you’ll need a connection to a telco that’s not over the cell network, usually they provide some sort of TCP interface for their SMS gateway, you can buy access to.

With high volume I mean anything where between 5-10 seconds by SMS (One SMS = 160 char, more chars is multiple messages glued together on the receiving end)

I’ve tried setting up smsd before on a Raspberry Pi, it’s quite easy, but the ZTE MF110 modems I used were quite unstable when I connected a handful of them through a USB hub. I was just toying around, and didn’t care much in regards to troubleshooting.

The disadvantages of using cell modems (Or cellphones acting as modems) are:

  • Slow transmission rate
  • No option to change the sender ID. (The phone number of the SIM will always be the sender)
  • High message cost, depending on the subscription, but generally this kind of usage will violate the ToS for most unlimited plans


  • Cheap initial investment
  • Easy to setup
  • Premade, rather cheap appliances exists, just plugin SIMs, and you have a gateway with an API to send messages.

Using a direct connection to a telco has the following disadvantages

  • High initial investment
  • High monthly fee
  • Requires a lot of development


  • High transmission rate (Usually multiple thousands of messages per sec)
  • Option to set the caller ID to ANYTHING you want. (Limited to 11 chars, when not using phone numbers)
  • Low cost per text, usually.
  • Usually allows you to resell capacity. (Eg. making a “send a text” service where third parties pay you for access)

What I would do, if I had a low volume, would be finding the cheapest SMS provider, that has the features I need, and an API I can use. Then send my texts that way. They are usually super simple to implement, and you can have multiple provides as a backup, if you need reliability.


I once did a job for a client involving setting up a custom SMS gateway for sending out messages to their users. The modem was a Sierra Wireless box. It happens to run Linux, and when you plug it in, it sets up a virtual LAN between itself and the host, so you don’t need special drivers.

I wrote custom Python code to act as the back-end server, receiving emails and forwarding them on as txts and also a web-based front end to monitor the process. There was no use made of Asterisk.

Receiving txts looked a bit more complicated–I think for that you have to write custom code that executes on the device.

1 Like

Not relate to Asterisk.

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