Online TCP & Proxy Port Checker

Updated: 2026-11-05

Before troubleshooting proxy authentication (407) or browser configuration errors, verify that the remote server's TCP port is actually reachable across the public internet. Enter any public IP or hostname and up to 8 TCP ports above to measure real three-way TCP handshake latency (SYN → SYN-ACK).

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Quick Presets:

Common Proxy & Server TCP Ports Reference

Different proxy daemons (Squid, 3proxy, Dante, HAProxy, Nginx) and server services listen on standard or high-range TCP ports:

TCP Port(s)	Common Protocol / Service	Typical Proxy & Server Usage
`8080`, `3128`, `8888`	HTTP / HTTPS CONNECT Proxy	Standard ports for Squid, 3proxy, and VinaProxy HTTP(S) gateways
`1080`, `1081`	SOCKS4 / SOCKS5 Proxy	Default listening ports for Dante and SOCKS5 relays
`80`, `443`	HTTP / TLS Web Server	Web servers, reverse proxies, and firewall-friendly proxy listeners
`10000–60000`	Dedicated High-Range Ports	Assigned to dedicated static IPv4 & ISP proxy allocations

Diagnosing 'Connection Refused' vs. 'Timeout'

OPEN (with ms latency): The remote host accepted our TCP SYN packet and returned SYN-ACK—the proxy daemon or service is actively listening.
CLOSED (refused): The host IP is online, but nothing is listening on that port (or an iptables REJECT rule sent a RST packet).
CLOSED (timeout): A firewall (AWS Security Group, UFW, Cloudflare, or ISP filter) silently dropped the SYN packet before reaching the application.

Step by step

1
Enter the target public IP or hostname
Paste your proxy server IP or VPS hostname into the 'Target Public IP' field.
2
Specify up to 8 TCP ports
Type comma-separated port numbers (e.g., 80, 443, 1080, 3128, 8080 or your specific assigned proxy port).
3
Click 'Check Ports' to run a live TCP probe
Our server initiates a real TCP socket connection to each port with strict SSRF protection.
4
Inspect Open/Closed status and handshake RTT
If the port is OPEN but your proxy still fails in a browser, verify your username:password credentials in our Proxy Checker.

Frequently asked questions

What is the difference between this Port Checker and the Proxy Checker?

The Port Checker tests Layer 4 TCP reachability (SYN / SYN-ACK) on any port without sending proxy credentials. The Proxy Checker tests Layer 7 proxy authentication (HTTP CONNECT or SOCKS5) and verifies the exit IP.

Why does the Port Checker block `127.0.0.1` or `192.168.x.x` addresses?

For security (SSRF protection), our server only dials public unicast internet addresses (isPublicIp) and refuses loopback, RFC1918 private LAN, and link-local ranges.

Why is my port OPEN here, but unreachable from my office Wi-Fi?

Corporate, university, or hotel Wi-Fi networks frequently block outbound connections to non-standard high ports (like 3128 or 30000+). Try switching networks or using a proxy listening on a standard port.