An SMPP keep-alive command exchanged periodically between an ESME and SMSC to verify that the connection is still active.
Why enquire_link Matters
An idle SMPP connection can sit for minutes without either side sending anything, and firewalls, load balancers, or NAT devices in between will often drop a TCP connection that looks inactive, without telling either endpoint. enquire_link exists so a dead connection gets detected in seconds rather than only surfacing the next time a real message fails to send.
How enquire_link Works
Either side, though typically the ESME, sends an enquire_link PDU on a fixed interval, commonly every 10 to 60 seconds. The other side must respond with enquire_link_resp; if no response arrives within a configured timeout, the session is treated as dead and the client re-binds.
How SMPPCenter Uses This
SMPPCenter's SMPP server sends and expects enquire_link on every idle bind, so a dropped connection is detected and cleared within seconds instead of waiting on a much slower TCP-level timeout.
Read More
Related Terms
FAQ
Frequently Asked Questions
Client Feedback
What Our Clients Say
Our clients run regulated, high-volume messaging infrastructure and prefer not to be named publicly. These testimonials are shared with permission while keeping commercially sensitive details confidential.
The migration was completed smoothly and the platform has remained stable under heavy production traffic. The flexibility of self-hosting was one of the biggest advantages for us.
High throughput, intelligent routing, and detailed monitoring have significantly simplified our messaging operations.
The delivery reports and routing controls give us the visibility we were looking for. The system has integrated well with our internal applications.
The platform has been reliable for business-critical messaging. Multi-connection support and detailed logging have made daily operations much easier.
Names and company details are withheld at our clients' request. This is common among telecom providers, SMS aggregators, fintech companies, and enterprises that consider their messaging infrastructure commercially sensitive.