Configure a TCP Connection Check

Monitor active TCP connections and detect connection exhaustion

Written By Erdinc Akay

Last updated About 2 months ago

Configure a TCP Connection Check

Add Check → TCP Connections with total thresholds 5000/10000, TIME_WAIT 1000/5000, CLOSE_WAIT 100/500.

A TCP Connection Check monitors the number of active TCP connections on a device, broken down by status. Too many connections — especially in TIME_WAIT or CLOSE_WAIT — indicate resource exhaustion, connection leaks, or application problems.

Prerequisites

  • You need the Monitoring Check Management permission. Your administrator assigns permissions under Administration → Groups.
  • The target device must have a connected agent.

Steps

  1. Go to Devices and open the device.
  2. Click the Checks tab → Add Check → TCP Connections.
  3. Configure the thresholds:
Total Connections Thresholds
FieldDefaultDescription
Warning total connections5000Warning when the total connection count exceeds this value
Critical total connections10000Critical when the total count exceeds this value
TIME_WAIT Thresholds
Warning TIME_WAIT1000Warning on excessive TIME_WAIT connections
Critical TIME_WAIT5000Critical on TIME_WAIT flood
CLOSE_WAIT Thresholds
Warning CLOSE_WAIT100Warning on connections stuck in CLOSE_WAIT
Critical CLOSE_WAIT500Critical on CLOSE_WAIT accumulation
  1. Click Add Check.

Tips

  • CLOSE_WAIT connections indicate that the application has not closed its side of the connection — this is almost always a bug. A low threshold (100) is appropriate.
  • TIME_WAIT connections are normal after closing short-lived connections — they prevent port reuse collisions. High numbers are only a concern on heavily loaded servers.
  • This check is especially useful on web servers, API servers, and database servers where connection exhaustion causes outages.

After the first check interval, the result appears in the device's Checks tab.

See also: TCP Connection Check Reference