TCP Port Checker

Test reachability of selected TCP ports with safe request limits
This free online tcp port checker runs in your browser and is part of our Developer Tools collection.

TCP Port Checker

Test whether selected TCP ports are reachable from this server with bounded, safe checks.

Maximum 20 ports per request.

What this helps with

  • Quickly verify service reachability from server perspective
  • Check expected open ports after firewall or SG changes
  • Practice basic network troubleshooting workflows
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Instant In-Browser Execution Runs locally in JavaScript without wait times or server delays.
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100% Privacy & Security Your inputs and files are never stored or logged on remote servers.
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Cross-Device Responsive Fully optimized for mobile smartphones, tablets, and desktop displays.
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100% Free Forever No subscription fees, no signups, and no software installations.

How to Use the Online TCP Port Checker

1 Enter Hostname or IP

Input the target server IP address or domain name.

2 Select Target Port or Service

Choose a common port preset (80 HTTP, 443 HTTPS, 21 FTP, 22 SSH, 25 SMTP, 3306 MySQL, 5432 PostgreSQL, 8080) or enter a custom port (1–65535).

3 Test Port Reachability

Click "Check Port" to perform an active TCP three-way handshake test.

4 Inspect Connection State

Review whether the port status is Open (listening), Closed (rejected), or Filtered (blocked by firewall/timeout).

Frequently Asked Questions

Common questions about using this free online tcp port checker.

What does an "Open" port mean? ▾
An Open port means a server daemon application is actively listening on that port and successfully completed the TCP three-way handshake (SYN, SYN-ACK, ACK).
Why does a port report as "Filtered" or "Timeout"? ▾
A Filtered status indicates that a firewall, cloud security group (e.g. AWS Security Group), or router dropped the probe packets without returning an RST rejection packet.
Can I test my home router port forwarding with this tool? ▾
Yes. Enter your public WAN IP address and target port (e.g. 25565 for a game server or 32400 for Plex) to verify that external traffic can reach your machine.
Are scan requests rate-limited to prevent abuse? ▾
Yes. Safe query boundaries and rate limits are enforced to protect network infrastructure.

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