Features How It Works Network Map Product News
Free Tools
Sign In Start Free

Is this port open?
Check from 28 locations.

Test if a specific TCP or UDP port is open and accepting connections from 28 servers across 16 countries. See exactly where a service is reachable, blocked, or filtered — without having to set up VPNs or run scripts from multiple regions.

28 Global Locations TCP & UDP No Account Required

Test if a specific TCP or UDP port is open and reachable from 28 worldwide locations. Enter any host plus a port between 1 and 65535 — results stream back per region in seconds.

Note: All checks are public. To keep your checks private, create a free account.

Global Network Diagnostics

Run a check to see your service from around the world.

  • Tested from 28 monitoring locations worldwide
  • Results in seconds, not minutes
  • Shareable result links for your team
  • No account or signup required

What is a Port Check?

Every network service runs on a numbered port — a logical endpoint that lets your operating system route incoming connections to the correct application. Web servers listen on port 80 (HTTP) and 443 (HTTPS), SSH daemons on port 22, and databases on their own dedicated ports. When you run a port check, you test whether that endpoint is reachable from the outside world.

TCP vs UDP

TCP (Transmission Control Protocol) is connection-oriented. To check a TCP port, a tool initiates a three-way handshake (SYN → SYN-ACK → ACK). If the remote server completes the handshake, the port is open. If it sends back a RST (reset) packet, the port is closed. If there is no response at all, the port is likely filtered — blocked by a firewall before the packet ever reaches the service.

UDP (User Datagram Protocol) is connectionless and harder to test definitively. A UDP port check sends a datagram and waits for a response or an ICMP "port unreachable" message. Silence can mean the port is open and the service is running, or it may mean a firewall is silently dropping packets — context and protocol-aware probing usually help disambiguate.

Port States Explained

Every port check returns one of three results. Open means a service is actively listening on the port and accepted the connection — your application is reachable. Closed means the host responded but no service is listening — the port is accessible but not in use. Filtered means a firewall, security group, or ACL blocked the connection and no response was received within the timeout window.

Common Reasons to Check a Port

Verify a newly deployed service is accessible after configuring firewall rules. Troubleshoot why users cannot connect to a database or API endpoint. Confirm a VPN or hosting provider is not blocking specific ports. Test whether a service is reachable globally or only from certain regions. Validate that a security configuration correctly blocks unauthorized ports.

Common Ports Reference

Use this table as a quick reference when checking the most frequently used TCP and UDP ports for common services.

Port Service Protocol Description
21 FTP TCP File Transfer Protocol — control channel for file transfers.
22 SSH TCP Secure Shell — encrypted remote login and command execution.
25 SMTP TCP Email sending — server-to-server mail transfer.
53 DNS TCP/UDP Domain Name System — hostname to IP address resolution.
80 HTTP TCP Web traffic — unencrypted hypertext transfer.
443 HTTPS TCP Secure web traffic — TLS-encrypted hypertext transfer.
3306 MySQL TCP MySQL database server connections.
5432 PostgreSQL TCP PostgreSQL database server connections.
6379 Redis TCP Redis in-memory data store and cache.
8080 HTTP Alt TCP Alternative HTTP port — common for dev servers and proxies.
8443 HTTPS Alt TCP Alternative HTTPS port — common for application servers.
27017 MongoDB TCP MongoDB document database server connections.

Why Check Ports From Multiple Locations?

A port that appears open from your office may be completely unreachable to users in other regions. Testing from a single location gives you an incomplete picture, and the failures it misses tend to be the most expensive: customers in one country quietly unable to reach your service while everything looks healthy from your laptop.

Multi-location port testing surfaces several distinct classes of issue. Geo-blocking — many organizations and cloud providers apply geo-based firewall rules that block traffic from specific countries or regions, so a port can be accessible from the US but blocked from Asia or Europe. ISP-level port blocking — internet service providers in certain countries block specific ports by default; port 25 (SMTP) is commonly blocked by residential ISPs worldwide to prevent spam, and testing from multiple ISPs surfaces these restrictions. Asymmetric firewall rules — firewalls often allow connections from known office or VPN IP ranges while silently dropping everything else, so what works from your laptop may be invisible to external users and customers. CDN and load-balancer routing — anycast load balancers and CDN edge nodes route traffic differently depending on the source region, so a port may be open on some edges but misconfigured or unavailable on others, causing intermittent failures for users in specific locations.

Emercom runs all 28 port checks in parallel from geographically distributed nodes, including locations in North America, Europe, Asia Pacific, South America, and the Middle East. You see the full picture in seconds rather than having to manually test from multiple tools or VPN endpoints.

Related Tools

More free network diagnostics, all running from the same 28-location footprint.

Website Availability Check

Test HTTP status codes, response times, and redirects globally.

Ping Test

Measure round-trip latency and detect packet loss from 28 global locations.

DNS Lookup

Query DNS records and verify propagation across regions.

WHOIS Lookup

Find domain registration details, expiry dates, and nameservers.

Want continuous port monitoring?

Monitor TCP and UDP ports automatically and get alerts when services become unreachable. 28 global locations. Under 30 seconds to alert.

Start Monitoring Free Open Full Tools