TCP Connect
Open one TCP connection to a host and port you choose, and see how long the handshake takes.
The check runs on your computer through the local agent. The host, the port and the result stay on this page.
Local agent
Paste the current code from the agent window. The field is cleared after each attempt.
Agent disconnected
Set up the agent
Download and start the local agent, then come back to this page.
About the agent and download- Start MyDevTools Agent. A private or loopback address needs the agent started with --allow-private.
- Copy the pairing code from the agent window.
- Paste the code below. If the browser asks for local-network access, allow it for this connection.
The browser sends the host, the port and the timeout only to the agent on 127.0.0.1. The agent opens one TCP connection and then closes it. It does not send data and it does not try a range of ports. The check does not go to a MyDevTools server. This browser remembers the timeout. It does not store the host, the port or the result.
Check
One host name or IP address. Private and loopback addresses need --allow-private. A port range is not accepted.
One port from 1 to 65535.
How long to wait for this one connection, from 200 to 10000 milliseconds.
Result
Check one host and one port to see the result.
- Address
- Time
On this page
TCP Connect asks the local agent to open one connection to a host and port you type, then closes it. The page shows whether it opened, was refused, timed out or had no route, and how many milliseconds that took. The grant is tcp.connect, separate from http.request, icmp.trace and dns.lookup.
Detailed Functionality
The agent resolves the name to the first address and applies the same destination rules as the HTTP client. Private and loopback addresses work only when the agent was started with --allow-private. Metadata, link-local and multicast addresses stay blocked, and the agent's own listening port is blocked. The check is a handshake only: no bytes are sent and no banner is read. A numeric range such as 80-443 is rejected. At most two checks run at once. The timeout stays in this browser. The host, the port and the result do not.
Practical Examples
example.comport 443 shows an open handshake and the time.127.0.0.1on a port with nothing listening shows a refusal.80-443in the host field is rejected. This is not a scan.
How to Use This Tool
Start the local agent
Download the agent, start it, and copy the pairing code.
Pair TCP connect
Paste the code and connect. The page asks for tcp.connect and keeps capabilities this browser already holds.
Check one port
Enter one host and one port, set the timeout, and press Check.
Read the result
The page shows the status, the address and the time. Copy it as text. Reloading the page clears it.
Tips and Best Practices
- A refused connection and a timeout are results. They are not a failed check.
- One request is one host and one port. A range stays out of this tool.
- At most two checks run at once.
- The published Windows download may be older than this page. TCP connect needs an agent that advertises tcp.connect.