NodeMCU captive portal webserver responds to HTTP, but not HTTPS - https

Question

I am setting up a captive portal similar based on this. My aim is to have anyone who connects be redirected and served the index.html page stored in the ESP8266's filesystem, from which they can navigate to other pages similarly stored. The code distinguishes between foreign sites and local sites by looking up the url in a text file named "urls.txt". Everything works fine, provided the user attempts to visit a pure-http site, but the user is not redirected when attempting to visit a HTTPS site. For example, attempting to connect to "www.google.com" would fail, but "www.nerfhaven.com" would succeed.
Here's some code from server.lua:
srv=net.createServer(net.TCP)
srv:listen(80,function(conn)
local rnrn=0
local Status = 0
local DataToGet = 0
local method=""
local url=""
local vars=""
conn:on("receive",function(conn,payload)
if Status==0 then
_, _, method, url, vars = string.find(payload, "([A-Z]+) /([^?]*)%??(.*) HTTP")
-- print(method, url, vars)
end
[...]
conn:send("HTTP/1.1 200 OK\r\n\r\n")
[...]
local foundmatch = 0
file.open("urls.txt", "r")
print("potato")
for i = 108,1,-1 do
line = file.readline()
--print(line)
if string.match(line, url) then
foundmatch=1
print("found " .. url)
end
end
print("potato2")
file.close()
[...]
conn:on("sent",function(conn)
print("sending data")
if DataToGet>=0 and method=="GET" then
if file.open(url, "r") then
file.seek("set", DataToGet)
local line=file.read(512)
file.close()
if line then
conn:send(line)
-- print ("sending:" .. DataToGet)
DataToGet = DataToGet + 512
if (string.len(line)==512) then
return
end
end
end
end
conn:close()
end)
end)
I would think this should work, as I see no way to discriminate between HTTP and HTTPS websites, and any of those should be simply chopped up and replaced with a local version (either index.html or something in urls.txt). Instead, it seems to send no response at all.

Answer 1

The code you shared only listens on port 80 - the HTTP port. It wouldn't be able to respond to HTTPS requests because HTTPS uses port 443.
So first, you'll need to listen on port 443 in addition to port 80.
Once you get a connection open on port 443 you'll need to run TLS (Transport Layer Security, the 'S' in 'HTTPS') and negotiate a secure connection before you can start handling HTTP over the secure connection.
NodeMCU does have a TLS library but it appears to only operate as a client, not a server, so unless you can find someone else who's done this you're on your own here, and it's a big project.
Assuming you get that working, any browser that connects to your "captive portal" is going to throw SSL certificate errors left and right because your server is doing exactly what TLS is designed to prevent - impersonating another web site. You won't have the certificates to prove you're www.google.com so the browser will strongly advise the user that something bad is happening and they shouldn't proceed.
Fundamentally and first, though, the reason you're not getting any answer for HTTPS is that you're not listening on the HTTPS port.