I think I have a general idea on how to implement basic TCP/IP sockets while staying true to QBasic 4.5's spirit (i.e. not introducing functions like _OpenConnection/_ConnectionAddress etc.)
The "API" I have in mind would look something like
```
OPEN "TCP:\127.0.0.1\80\LISTEN" FOR INPUT AS #1
INPUT #1, CONN$
IF CONN$ <> ""
REM CONN$ contains something like "TCP:\127.0.0.1\80\REMOTE_HOST\REMOTE_PORT"
OPEN CONN$ AS #2
REM ... respond to request
PRINT #2, "200 OK"
CLOSE #2