Instructions for Master Server Error: <!DOCTYPE html>

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(Tools for Sonic Team Junior: at the bottom.)

Prerequisites (do not skip): You should verify that the master server's address in Server Options in SRB2 matches exactly the address written here and/or here and then try again connecting to the master server before proceeding; you must be registered on this forum in order to request help from STJr. The following instructions are applicable to SRB2 only, not SRB2Kart; unless specifically requested by Kart Krew or STJr, you shouldn't need to follow these instructions.

Problem description: Whenever trying to connect to the master server of SRB2, you get an error in the console with the message "<!DOCTYPE html>".
Cause: Not your fault (this has nothing to do with port forwarding, which you may or may not need to do nevertheless). Cloudflare (the CDN company that SRB2 uses for the domain, which is shared by the forums and the master server's address) intercepts your connection to the master server and subjects you to excessive anti-bot "challenges" in the form of HTML webpages intended to be loaded in a Web browser, but since SRB2 is not a Web browser, it doesn't understand the HTML webpage it receives from Cloudflare.

Resolution: After you've read the prerequisites above, create a new private thread describing the specific error you've got and include your Cloudflare's Ray ID. (You should post privately in order to not clutter the forums. Nevertheless, posting your Ray ID in public should not compromise your privacy; it's meaningful only to Sonic Team Junior.) Follow the following instructions step-by-step to collect a Ray ID for example:
  1. Open Wireshark. If you don't have Wireshark installed on your computer, refer to its official website at (Wireshark is free as in freedom, and shouldn't have any viruses or malware included. The screenshots below were taken on Windows, but Wireshark is compatible with all computer operating systems.) A list of the network interfaces/adapters will be displayed. You need to prepare to click on the interface which is used to access the Internet; this is usually the interface with the most activity happening (as shown in the graphs besides the interfaces' names in the list). (You can try opening some website to see which of the graphs spikes up.) Do *NOT* choose the "adapter for loopback traffic"!
  2. Open SRB2. Go to the server options and change the master server's address to use plain HTTP instead of HTTPS, leaving the rest of the master server's address unchanged (although you may have to erase and retype it by hand). The address shown in the screenshot may be outdated.
  3. Go to the multiplayer menu and prepare to press Enter and browse the master server.
  4. Switch (by pressing Alt-Tab) from SRB2 to Wireshark, and double-click on the network interface used for Internet access. The title of the window should say "Capturing" and the STOP button should be available for clicking on.
  5. Switch back to SRB2, press Enter to browse the master server, wait for the error to show up, and immediately switch back to Wireshark and press the STOP button.
  6. In the filter/search bar (the one that says "apply a display filter..."), type the following expression and press Enter:
    tcp.port == 80
    Search for an HTTP packet that says "GET /MS/0/...", right-click on it, and select Follow -> HTTP Stream.
  7. A new window will open with the raw data transmitted between SRB2 and the master server. In the server's response, you will see the Ray ID ("CF-RAY") that Cloudflare assigned to you for this specific connection. Copy the entire Ray ID, including the three letters at the end (e.g. 0123456789abcdef-ABC), and include it in your post.

Tools for Sonic Team Junior:
You can check for the subnet prefixes and ASNs of IP addresses, along with other information:
You can check for the presence of IP addresses in Spamhaus's anti-spam blacklists:
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