Ussd server

Implements a USSD application over SMPP: receives USSD requests from the SMSC/USSD gateway, emits them to the flow, and sends back the response messages the flow produces. Use it to build USSD menus (e.g. *123#).

Pins

Pin	Kind	Types	Description
Start	start	-	Opens the SMPP session. Called by the system when the flow starts if it is not connected.
Request	output	Viaducta.Plugins.Smpp.Types.UssdMessage	One message per incoming USSD request.
Response	input	Viaducta.Plugins.Smpp.Types.UssdMessage	Connect the component that produces the answer; every message received here is sent to the gateway.

UssdMessage: Operation (USSD service operation, int), MessageText, Sender, Receiver.

Operation values: 0 PSSD_INDICATION, 1 PSSR_INDICATION, 2 USSR_REQUEST, 3 USSN_REQUEST, 16 PSSD_RESPONSE, 17 PSSR_RESPONSE, 18 USSR_CONFIRM, 19 USSN_CONFIRM, 34 USER_EXIT.

Configuration

Field	Type	Default	Description
Host	string (required)	localhost	SMSC / USSD gateway host.
LocalEndpointIp	string	Any	Local IP to bind the socket to.
Port	integer 1-65535	10000	Gateway port.
AddressRange	string, max 41 chars	empty	ESME address range (e.g. the service code).
SystemId	string, max 32 chars	empty	SMPP system_id.
Password	password	empty	SMPP password.
SystemType	string	ESME	SMPP system_type.
EnquireLinkInterval	integer seconds, max 60	5	Keep-alive interval.
GeneralTimeout	integer seconds, max 300	5	Response timeout.
SourceAddressNpi	dropdown: 0 Unknown, 1 ISDN, 3 Data, 4 Telex, 6 LandMobile, 8 National, 9 Private, 10 ERMES, 14 Internet	8	Numbering plan of the response Sender.
SourceAddressTon	dropdown: 0 Unknown, 1 International, 2 National, 3 NetworkSpecific, 4 SubscriberNumber, 5 Alphanumeric, 6 Abbreviated	3	Type of number of the response Sender.
DestinationAddressNpi	dropdown, as SourceAddressNpi	1	Numbering plan of the response Receiver.
DestinationAddressTon	dropdown, as SourceAddressTon	1	Type of number of the response Receiver.
DataCodingType	dropdown: 0 SMSCDefault, 1 IA5_ASCII, 3 Latin1, 8 UCS2, ... (same list as Sms transmitter)	0	Encoding of the response text.

Behaviour

• On Start the plugin binds as transceiver with SMPP 3.4 and starts reading; the flow keeps running.
• Each incoming deliver_sm / data_sm becomes a UssdMessage (Operation from the ussd_service_op parameter, 0 if missing) with new metadata on Request.
• Every message arriving on Response is sent as submit_sm with service type USSD and ussd_service_op = Operation. A rejected submit is logged as an error.

Notes

• There is no session handling: build the response yourself. Swap the addresses (Receiver = request Sender, Sender = request Receiver) and choose the operation: typically 17 (PSSR_RESPONSE) to answer and end, 2 (USSR_REQUEST) to show a menu and wait for the next input. Keep menu state yourself (e.g. keyed by the subscriber number).
• Messages sent to Response before the session is open fail.
• Errors in the read loop and in downstream components are swallowed silently.
• Ports above 32767 are not handled correctly (converted to a 16-bit signed number).
• Use an expression setting (=Secrets.UssdPassword) for Password.

Example

{ "Host": "ussdgw.example.com", "Port": 2775, "SystemId": "ussdapp", "Password": "=Secrets.UssdPassword", "AddressRange": "\\*123#", "DataCodingType": 0 }

Ussd server (Request) → C# script (build menu, swap addresses, Operation = 2 or 17) → Ussd server (Response)