Receiving SMS over SMPP

Question

I have a project coming up where I need to send and receive messages through a specific mobile operator, which only provides an SMPP interface. The whole project will be a hosted website. I have already read quite a lot, but I do not yet quite understand what is actually needed from my side to use the protocol.

Should my application try to maintain a constant connection to the smpp? Can I simply connect, send a message and then disconnect?

Are receiving messages based on push or pull?

Thanks for the help.

Answer 1

SMPP is a peer-to-peer protocol. That should mean that SMS Gateway (your side) and SMSC (your mobile operator) need to have a proper bind/connection established. Even when there are no SMS or DLRs to send/receive, there is a continous exchange of smpp PDU (enquire_link/enquire-link_resp) that ensure that the bind is established. In detail, if you send an enquire_link PDU and you get no response (enquire_link_resp) the bind is broken. Your sms won't be delivered (will remain enqueued in your gateway store), and you won't receive MOs (incoming sms) or DLRs (delivery report). To re-establish the connection you should re-initiate the connection.

So, my answer would be that you need a constant connection to SMSC.

Answer 2

You are stating you want to receive messages, as a result at least a bind_receiver is needed. Because you don't know when messages are going to come in, you will have to be constantly connected, rather than disconnecting after each event.

With regards to your question about "push or pull" this depends on how you solve the first problem. If you can build a solution that is constantly connected, the result will be a push (the carrier will push it to you as soon as they receive the message). If (for some reason) you cannot maintain a constant connection, you'll end up building a pull mechanism. You'll connect to the carrier ever X seconds to see if they have a message waiting for you.

I do need to highlight 2 pitfalls though:

1. A number of carriers in the world, do not store or even accept messages if you are not connected, therefore, depending on which carrier you interact with, you might be forced to use a continuous connection.
2. Most carriers do not allow you to open and close connections in quick succession. Once you disconnect, you can not reconnect for a time frame of X seconds.

Therefore a constant connection is really the way to go. Alternatively, you can look into a company like Nexmo, which will provide you with a HTTP Call every time a message arrives.

I'm not sure which language your developing your application in, but if you use any of the popular languages (Java, PHP, Perl) there are modules out there that handle basic SMPP Connectivity for you. A quick google search for your language and "SMPP Client" will give you a list of references.