Editing External Short Messaging Entity (section)

==Routing in SMSC for ESME==
An example of how the routing can be done at SMSC level, but not mandatory as this depends a lot on the implementation of SMSC and the way the connection inside the SMSC is between routing part of the SMSC and SMPP interface can be as below:
During the service agreement between ESME and service provider (SMSC side) one unique short code will be allocated to ESME. At the SMSC end smpp server will have list of all ESME address and active connection. When any message gets sent to short code, messages first comes to SMSC, SMSC decodes it according to GSM 3.4 spec, then one of the modules in SMSC checks the destination address and if it is short code then that module routes messages to SMPP server part of the SMSC. Now SMPP server will have all active connection, according to destination address it selects the ESME - SMPP server connection object, that object will be responsible to encode message according to SMPP protocol and forward to ESME.

Communication between SMSC and ESME can be on either SMPP or HTTP.
If one has a SMPP account, they could connect to the SMPP IP+Port on TCP/IP and the SMPP will push MOs to ESME on SMPP connection, and ESME will push MTs on the same connection in reverse.
If they have a HTTP account with the operator's SMSC, then the SMSC will submit MO to a given URL and to push MTs SMSC will be given on URL.