SMSC is having multiple connections with client Bu

I am having a strange issue. I am working on sms module for one of the client.

So, I am using Kannel to connect to SMSC server. At the very first attempt means after restarting both client and server applications . I am able to connect to SMSC with one active connections but, after some time server is having multiple connections for My IP although i am having only one connection at that time . Because , of this we are not able to receive MOs properly there is a huge MO drop. To overcome this problem we has to restart both client and server applications frequently. Which is not a proper solution So, server requested me to resolve our end as they have multiple partners and they are not facing this issue.

Background :

Before , they have provided us a ip(public ip) and port to connect to SMSC .Asked our IP(public ip) to make whitlist at their end. And they have provided VPN settings after VPN configured we are successfully connected to SMSC. They have masked our IP at their end to treat as local IP.

So, Please help me to resolve this multiple connections error as i am new to kannel and SMPP.

I had the same exact issue with another SMPP client app, it was NowSMS, and also, it was very strange as my NowSMS is connected to +15 SPs since 7 years ago, and I had no such issue with anyone of them. But, NowSMS told me that there's an understandable issue at SP's side and after a some investigations, we noticed that the SP deals with the first established connection only and ignores the other connections, although, I had one single connection only and all previous connections were closed from my side before establishing a new one. So, please discuss the same with your SP, otherwise, share the full config here as you may have something incorrect.

BTW, did you try getting a live TCP trace from your side and SP's side at the same time?