Thanks. If I set os.dupterm(None), I get a telnet login on WLAN which works OK ('Login succeeded!), but no REPL '>>>' on WLAN (or UART0) as might be expected. micropython.org indicates dupterm requires a stream_object. I have tried the obvious wlan and server instances without success. What is the relevant object here?

@fsergeys Is there a particular reason you need to capture stdout/stderr vs. just writing your log straight to the file?