Sorry I have no ready to use code.
You have to prepare User Data your self. Refer to 3GPP TS 23.040 http://www.3gpp.org/ftp/Specs/archive/2 ... 40-660.zip
Read chapter 9.2.3.24. There is a description how to create EMS messages.

Could you show me the values of the following variables:
orgTon, orgNpi, destination, desTon, desNpi, msisdn, msgBody

yes, you can detect it by checking property MessageType in a DataSm or DeliverySm opertaions.

It looks like everything correct.
Any problems?

EnquireLink is used to provide a confidencecheck
of the communication path between an ESME and an SMSC.
If your SMSC sends this message, ALT.SMS.SmppClient responds immediately. You can track this in the evEnquireLink event.
Or you can send your EnquireLink request at any type, use method ...

Yes, you can use ALT.SMS.SmppClient library free of charge in your commercial applications. There are no restrictions.

Only source code of this library have cost.

HostName is domain name or ip address of SMSC (short message service center).
You have to ask mobile operator to give you SystemId and Password to bind with SMSC.

you can use SmppClient.ShortMessageMaxBytes to increase bytes number in message_payload field or in short_message for one part of SubmitSm. Default is 140 bytes.
But maximum length depends on SMSC you connect to.

Version with ASCII encoding now available.

You can download ALT.SMS.SmppClient 1.2 + Demo for .NET 1.1 , 2.0 and Mono

Please test it.

When you use ShortMessage mode, you send long messages with altered UDHI flag, message parts in short_message field and reference number in its User-Data-Header.
When you use Payload mode, you send long messages in the optional parameters message_payload, sar_msg_ref_num, sar_total_segments, sar ...

You can buy source codes at ShareIt Order Page

I have released version 1.1.1 where you can try SubmitText with SubmitMode.Payload

Sorry, it is not implemented yet, but in process...

It is known that parameter "message_payload" can contain user data up to 64K, but some servers doesn't allow to send such a big message in one packet.

How many bytes in message_payload your server accepts?

I have unfinished method SubmitText ...

sorry it is not open source library.
You may use ALT.SMS.SmppClient for free
but source code is not free.

As for SMPP 5, I have no available connection to test this specification.

Sorry, documentation in process

You can check Demo application (sources included) at
http://www.inetlab.ru/en/ALT.SMS.SmppClient