---
title: "JMeter java.net.ConnectException"
description: "Fix JMeter java.net.ConnectException: wrong host or port, firewall, TLS mismatch, timeouts, and injector network path. Symptom, causes, and ordered fixes."
url: https://docs.jmeter.ai/topics/errors/connect-exception/
lastUpdated: 2026-10-01
source: docs.jmeter.ai
---

# JMeter java.net.ConnectException

## Symptom

In View Results Tree, the JTL, or dashboard error tables you see messages such as:

- `java.net.ConnectException: Connection refused`
- `java.net.ConnectException: Connection timed out`
- `Non HTTP response code: java.net.ConnectException`
- Sample marked failed with **no** normal HTTP status (not 200/404/500)

Often every thread fails immediately, or failures start when the system under test (SUT) or network path is wrong.

## Common causes

| Cause | Why it happens |
| --- | --- |
| Wrong host, port, or protocol | HTTP Request Defaults / sampler still point at lab host or `http` vs `https` |
| Property not applied | Plan uses `\${__P(host,)}` but CLI omitted `-Jhost=...` ([functions](/topics/functions-and-variables/)) |
| SUT not listening | Process down, wrong interface, or container port not published |
| Firewall / security group | Injector cannot reach SUT (common in CI and [Kubernetes](/topics/docker-kubernetes/)) |
| Connect timeout too short | Network latency or cold start exceeds HTTP Request connect timeout |
| Distributed workers differ | Workers lack DNS/route the controller has ([distributed testing](/topics/distributed-testing/)) |

## Fix (ordered)

1. **Copy the exact error** from the first failed sample (code + message).
2. **From the same machine that runs JMeter**, test reachability (`curl`, `Test-NetConnection`, browser). If curl fails, it is not a JMeter sampler bug.
3. Open **HTTP Request Defaults** and the failing sampler: protocol, server name, port, path. Prefer one defaults element so hosts stay consistent ([web test plan](/user-manual/build-web-test-plan/)).
4. If the plan uses properties, print the effective command:

```bash
jmeter -n -t plan.jmx -Jhost=staging.example.com -Jport=443 -l out.jtl -j jmeter.log
```

Confirm `\${__P(host,localhost)}` (or similar) is what you intend.
5. Raise **connect** and **response** timeouts only after host/port are correct.
6. On CI/K8s: check NetworkPolicy, egress, private DNS, and that the job runs in a network that can see the SUT ([CI/CD](/topics/ci-cd-load-testing/)).
7. Distributed: reproduce **on a worker** shell; fix worker networking and data, not only the controller ([remote testing](/user-manual/remote-test/)).

## Related tools and topics

| Resource | Use when |
| --- | --- |
| [Non HTTP response code](/topics/errors/non-http-response-code/) | Broader non-HTTP failures |
| [SSLHandshakeException](/topics/errors/ssl-handshake-exception/) | Connect works but TLS fails |
| [GUI works, CLI fails](/topics/errors/gui-works-cli-fails/) | Host only wrong under CLI |
| [Docker / Kubernetes](/topics/docker-kubernetes/) | Container networking |
| [Troubleshooting overview](/topics/troubleshooting/) | Full triage tree |

## Frequently asked questions

### Is ConnectException an HTTP 500?

No. It usually means JMeter never completed a normal HTTP exchange. The failure is at the TCP/connect layer (or is wrapped as a non-HTTP sample error).

### Why does it work on my laptop but fail in CI?

CI runners often cannot reach private staging hosts, or `-Jhost` / secrets differ. Test connectivity from the runner image first.

### Should I increase threads to fix Connection refused?

No. Connection refused means nothing accepted the socket. Fix host, port, process, or firewall first.

## Continue Learning

→

### Next Practical Step

From the injector host, curl the same URL JMeter uses; only then adjust the sampler or `\${__P(host)}`.

📖

### Related Reference

- [API load testing](/topics/api-load-testing/)
- [Best practices](/user-manual/best-practices/)
- [Distributed testing](/topics/distributed-testing/)