ephemeral-port-reserve
Bind to an ephemeral port, force it into the TIME_WAIT state, and unbind it.
Decision gist · record as of 2026-08-14
Yes, if you need race-free ephemeral port allocation in parallel or containerized scenarios where port 0 doesn't work. The package is lightweight, has no dependencies, carries a permissive license, and is actively maintained. Install it only if you hit the specific problem it solves; it's not a general-purpose utility.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires a Unix-like system with socket support; behavior and grace period (default 60 seconds on Linux) are OS-dependent.
- No runtime dependencies and low install friction.
- Repository is active with recent commits (last commit 2026-04-02) and has been maintained since 2016, though the latest release was 2021-02-11.
License · maintenance · safety
MIT (permissive) — MIT license is permissive and imposes no restrictions on use, modification, or distribution in proprietary or open-source projects.
last release 2021-02-11 (2010 days) · last repo commit 2026-04-02 · 70 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 90,223 downloads/mo, #13,610 on PyPI
Alternatives
Verify before relying
pip install ephemeral-port-reserve
from ephemeral_port_reserve import reserve
port = reserve()
print(port) # Returns an available port number- Whether the package works reliably on Windows or other non-Linux systems.
- Current test coverage and whether the race-free guarantee holds under high concurrency.
- Whether the 60-second TIME_WAIT grace period is configurable or system-dependent only.
What it is and what it does
ephemeral-port-reserve solves the problem of allocating unused network ports when the standard "port 0 trick" fails or is unreliable. Some applications like mysqld or Docker interpret port 0 specially rather than letting the kernel choose a free port, and Docker's port allocation can race under parallelism. This package provides a race-free alternative by binding to an ephemeral port, forcing it into TIME_WAIT state, and unbinding it—reserving that port so the kernel won't reuse it for a grace period (typically 60 seconds on Linux), while still allowing subprocesses to bind to it explicitly if they use SO_REUSEADDR.
It's typically used in test suites, containerized deployments, and parallel service startup scenarios where you need to guarantee port availability without hard-coding. The package has no runtime dependencies, supports Python 2.7 and 3.5 through 3.8, and is maintained as a small, focused utility.
Use it for
- Running multiple Docker containers in parallel without port conflicts by reserving ports before container startup.
- Allocating ports for parallel test services in CI/CD pipelines where port 0 is unreliable.
- Starting multiple instances of mysqld or similar daemons that don't honor port 0 as a kernel-allocation signal.
- Ensuring port availability in containerized test environments where standard ephemeral allocation races.
- Scripting port reservation for subprocess startup when you need to pass the port number to child processes.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you need race-free ephemeral port allocation in parallel or containerized scenarios where port 0 doesn't work.
The package is lightweight, has no dependencies, carries a permissive license, and is actively maintained. Install it only if you hit the specific problem it solves; it's not a general-purpose utility.
Install
ephemeral-port-reserve on PyPI
Before you install
No runtime dependencies and low install friction. Repository is active with recent commits (last commit 2026-04-02) and has been maintained since 2016, though the latest release was 2021-02-11.
Requires a Unix-like system with socket support; behavior and grace period (default 60 seconds on Linux) are OS-dependent.
License in practice
MIT license is permissive and imposes no restrictions on use, modification, or distribution in proprietary or open-source projects.
Quickstart
pip install ephemeral-port-reserve
from ephemeral_port_reserve import reserve
port = reserve()
print(port) # Returns an available port numberVerify before relying
- Whether the package works reliably on Windows or other non-Linux systems.
- Current test coverage and whether the race-free guarantee holds under high concurrency.
- Whether the 60-second TIME_WAIT grace period is configurable or system-dependent only.
Package facts
| License | MIT permissive |
| Python support | Supports the current Python release !=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,>=2.7 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 2,010 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 90,223 / month, #13,610 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | License :: OSI Approved :: MIT LicenseProgramming Language :: Python :: 2Programming Language :: Python :: 2.7Programming Language :: Python :: 3Programming Language :: Python :: 3.5Programming Language :: Python :: 3.6Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8Programming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPy |
Evidence: ephemeral_port_reserve-1.1.4-py2.py3-none-any.whl
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