STATUS_ADDRESS_CLOSED (0XC000020B) Fix – Transport Address Now Closed

The 30-Second Fix: Reboot and Release Your IP

This error shows up when a network address—like a port or IP—gets stuck in a closed state after an app or service crashes. I've seen it most often with OpenVPN connections that disconnect abruptly, or after an RDP session drops without warning. The quickest way to shake that loose is to flush your network settings.

1. Open Command Prompt as admin. Click Start, type cmd, right-click it, and pick Run as administrator.
2. Type ipconfig /release and press Enter. You'll see your network adapters drop their IPs—expect a message like "No operation can be performed on Local Area Connection while it has its media disconnected" if you're on Wi-Fi. That's fine.
3. Type ipconfig /renew and press Enter. This grabs fresh IPs from your router. It might take 5–10 seconds.
4. Type ipconfig /flushdns and press Enter. Clears the DNS cache—sometimes stale entries cause this.
5. Restart your computer. Not optional—this step forces the network stack to rebuild. After the restart, try whatever app gave you the error. For me, this fixed a stuck RDP session in about 90 seconds total.

If it didn't work, move to the next fix.

The 5-Minute Fix: Reset Winsock and the TCP/IP Stack

Still seeing 0xC000020B? The transport address is probably stuck in the Windows Sockets (Winsock) catalog. This happens a lot after a VPN client uninstalls badly or a security suite messes with network filters. Here's how to reset it.

1. Open Command Prompt as admin again.
2. Type netsh winsock reset and press Enter. You'll get a message: "Successfully reset the Winsock Catalog." Then it'll tell you to restart.
3. Type netsh int ip reset and press Enter. This resets the TCP/IP stack. Expect: "Resetting Global, OK!" for each entry.
4. Type netsh int ipv6 reset and press Enter. Same deal—resets IPv6 stack. You'll see OK messages.
5. Restart your machine. Don't skip it—the changes only take effect on boot.

After the restart, test your app. If you're still hitting the error, the network stack itself is likely corrupted. That's the next level.

The 15-Minute Fix: Check for Port Conflicts and Corrupted Drivers

This error can also mean something already owns the address you're trying to use. For example, if you're running a web server on port 443 and another app tries to grab it, you'll get STATUS_ADDRESS_CLOSED. I've also seen it with a broken network driver after a Windows Update.

Step 1: Find the Conflicting Process

1. Open Command Prompt as admin.
2. Type netstat -ano | findstr : (replace with the actual port number from the error, like 3389 for RDP). Press Enter. You'll see a list of processes using that port, with a PID at the end.
3. Note the PID. Then type tasklist | findstr —this shows the program name. If it's something like svchost.exe, that's normal but might indicate a hung service.
4. To kill it, type taskkill /PID /F. That forces it to stop. Try your app again.

If you can't find a conflicting process, move to the driver check.

Step 2: Reinstall Your Network Adapter Driver

A corrupted or outdated driver can leave addresses in a half-closed state. Here's a clean reinstall.

1. Press Win + X and pick Device Manager.
2. Expand Network adapters. Find the one you're using (likely Intel, Realtek, or Qualcomm).
3. Right-click it and select Uninstall device. Check the box "Delete the driver software for this device" if you see it. Then click Uninstall.
4. Restart your computer. Windows will automatically reinstall the driver. This usually takes one boot cycle—maybe 2–3 minutes.
5. After boot, test your app. If the driver reinstall didn't help, try a manual driver update from the manufacturer's website instead of Windows Update. I've seen Realtek drivers from 2022 cause this on Windows 11 23H2.

Still stuck? Then it's likely a deeper issue with a specific application. Check the app's logs—many VPNs and remote desktop tools log the exact address that's closed. Reinstalling the app often clears the cached state.

When to Just Restart Everything

If none of these work, a full network reset might be your only option. In Windows 10 and 11, go to Settings > Network & Internet > Advanced network settings > Network reset. Click Reset now. This wipes all your network adapters and settings—you'll have to reconnect to Wi-Fi and reconfigure VPNs. But it's saved me twice when nothing else did.

That's the whole playbook for 0xC000020B. Start with the reboot and flush, then try Winsock, then dig into port conflicts and drivers. You'll almost always catch it by step two.