I’ve been playing Langrisser Mobile for years. It’s one of those games that I keep coming back to — but recently I ran into a puzzling problem: I couldn’t log in anymore.

Every attempt to log in would end with an “unknown error.” Even trying the QR code login option failed, leaving me locked out of the game.

I contacted official support, and their advice was pretty simple: “Try using a VPN or cellular data.” Sure enough, the game worked fine on a VPN or my phone’s hotspot. But that’s not a real fix — and I was curious enough to dig into what was really happening. This post is the story of how I debugged it.

First Suspicions: Something Wrong With HTTPS

When something works on one network (VPN, cellular) but fails on another (home Wi-Fi), the issue usually isn’t the game servers themselves. It’s network path specific.

It took me quite a while to figure out the right path forward. At first, I wasn’t even sure where to start.

1. I ran the site through SSL Labs’ SSL Server Test. The result came back with a Grade B. The certificate was issued by DigiCert, trusted by all major stores, and valid until September 2025. There were no revocation or chain issues. → That reassured me that the problem wasn’t a broken certificate or an expired cert at the server side.
2. I confirmed the exact same SSL error in both Windows PowerShell and WSL (Linux), so it wasn’t just a client quirk.
3. I also checked that I had no proxy configured, just to eliminate man-in-the-middle software on my machine.
4. To be extra sure, I tried manually accessing one of the game’s static resources:

   https://media.zlongame.com/media/common/js/qrcode/qrcode.js

   The JavaScript for generating the login QR code loaded just fine. That told me the CDN itself was up and reachable, so the issue wasn’t just “the servers are down.”
5. Finally, I dug into the local game logs, located at:

   C:\Users\admin\AppData\LocalLow\BlackJack\Langrisser\Log

   There, I spotted repeated access errors when the client tried to reach us-member.zlongame.net.

With all that ruled out, I started to zero in on the login API calls. The failures seemed specific to HTTPS requests to that domain — which pointed me squarely back toward an SSL/TLS problem.

Step 1: Testing With OpenSSL

Here’s the command I ran to manually start a TLS handshake:

openssl s_client -connect us-member.zlongame.net:443 -servername us-member.zlongame.net

And here’s what came back on my home network:

4097852DCC740000:error:0A00010B:SSL
routines:ssl3_get_record:wrong version number:
../ssl/record/ssl3_record.c:354:
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 5 bytes and written 324 bytes
Verification: OK
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)
---

Only 5 bytes were read before the connection failed. That usually means I’m sending a TLS handshake, but the other side is replying with something that isn’t TLS at all — often plain HTTP.

Step 2: Forcing the IP and Comparing

The domain us-member.zlongame.net is fronted by Cloudflare. A quick dig confirmed it:

dig +short A us-member.zlongame.net
us-member.zlongame.net.cdn.cloudflare.net.
104.18.30.145
104.18.31.145

To eliminate DNS variance, I tested directly against the IP:

curl -vk https://us-member.zlongame.net/ \
  --resolve us-member.zlongame.net:443:104.18.30.145

On my home network, this failed with the same wrong version number error.

But on VPN or cellular, the exact same command worked:

* SSL connection using TLSv1.3 / TLS_AES_256_GCM_SHA384
* Server certificate:
*  subject: CN=*.zlongame.net
*  issuer: DigiCert Inc
< HTTP/2 404
< server: cloudflare

So Cloudflare was serving a valid certificate when accessed via a different path. This confirmed the problem was network-path specific.

Step 3: Looking at the Network Path

Next, I compared traceroutes from the failing and working networks.

Bad path (Comcast):

 3  10.60.232.195 ...
 4  po-320-322-rur202.sanjose.ca.sfba.comcast.net ...
 9  be-39931-cs03.9greatoaks.ca.ibone.comcast.net ...
13  104.18.30.145

Good path (VPN via Cogent):

 6  be2820.agr21.sjc13.atlas.cogentco.com ...
 7  be5973.ccr81.sjc13.atlas.cogentco.com ...
11  104.18.30.145

Both routes ended at the same Cloudflare IP, but only the Comcast path failed.

At this point, I was convinced something in Comcast’s chain was interfering with TLS.

Step 4: Investigating My Gateway

I checked my Xfinity gateway’s web UI. The firewall was already set to Minimum Security, so that wasn’t the culprit.

Then I remembered: Comcast enables a feature called xFi Advanced Security by default, which inspects and filters HTTPS traffic.

But here’s the trick — you can’t see or toggle it in the web interface. It only shows up in the Xfinity mobile app.

Step 5: The Real Culprit — xFi Advanced Security

Sure enough, in the Xfinity app under Services → xFi Advanced Security, I found the feature enabled. This setting transparently inspects HTTPS traffic and sometimes injects HTTP responses instead of completing the TLS handshake.

That perfectly explained why openssl kept seeing wrong version number: I wasn’t actually talking to Cloudflare — I was talking to Comcast’s middlebox.

I disabled Advanced Security, rebooted the gateway, and reran my curl test:

curl -vk https://us-member.zlongame.net/ \
  --resolve us-member.zlongame.net:443:104.18.30.145

And just like that — success! Full TLS handshake, Cloudflare cert, and a clean HTTP/2 response.

Langrisser Mobile login worked normally again.

Lessons Learned

1. If TLS fails only on one ISP, suspect a middlebox. The servers and certificates were fine — the problem was Comcast intercepting traffic.

2. wrong version number usually means “not TLS at all.” If you see it, the other end might be sending back HTTP or a block page on port 443.

3. ISP “security” features can break things. xFi Advanced Security sounded helpful, but in practice it was blocking a legitimate game login API.

4. VPNs work because they tunnel around middleboxes. That’s why support suggested VPN/cellular — those routes bypass Comcast’s HTTPS inspection.

Closing Thoughts

For me, the end result wasn’t just being able to log into Langrisser Mobile again — it was the reminder that debugging network issues can be a detective story. Sometimes the villain isn’t the app or the server, but your ISP’s “helpful” security features.

Next time you see mysterious SSL errors, remember: it might not be the game. It might be your router trying to be too smart.