QUERY · ISSUE

and RFC2217 connections

openby Josverlopened 2026-01-07updated 2026-01-07

bugtools

Port, board and/or hardware

Any platform - affects mpremote tool when connecting via socket:// or RFC2217

MicroPython version

mpremote 1.27.0
Tested against MicroPython unix port 1.27.0 via
- socket://localhost:port
- rfc2217://localhost:2217

Reproduction

1 unable to mount host filesystem over socket connections

mpremote connect socket://localhost:2218 mount .

AttributeError: 'SerialIntercept' object has no attribute 'in_waiting'

2 Incorrect newline handling in interactive repl over socket

Connect to MicroPython Unix port:

mpremote connect socket://localhost:2218 repl

Type commands and observe output appears like:

>>> print("hello")
                   hello
                         >>>

3 repl over socket://

mpremote connect socket://localhost:2218 repl

REPL may fail to respond or hang

4 repl over rfc2217

mpremote connect rfc2217://localhost:2217 repl

Output may be delayed, laggy, or appear in bursts
pyserial's RFC2217 implementation uses a background thread to process telnet data from the socket into an internal buffer. When mpremote's REPL loop uses select() on the socket, it signals "ready" when data arrives, but inWaiting() returns 0 because the background thread hasn't processed the data yet.

Race condition sequence:

select() returns because socket has data
inWaiting() returns 0 (background thread hasn't processed yet)
REPL loop skips reading
Next iteration: select() returns, now inWaiting() > 0
Finally reads the data

This causes noticeable lag and stuttering in the REPL.

Expected behaviour

mpremote should work correctly with socket-based connections (socket://, RFC2217), providing:

Functional mount operations
Proper newline handling in REPL output
Responsive REPL without lag or race conditions

Observed behaviour

Mount operations fail with AttributeError
REPL output has "staircase" effect (misaligned lines)
REPL may hang or fail to get input from socket connections
REPL output is laggy/stuttering with RFC2217 connections

Additional Information

aeb1ce6 - Add in_waiting property to SerialIntercept class
2d46d52 - Fix REPL newline handling
7f0abfd - Improve waitchar() wrt socket connections
1ff555c - Fix REPL race conditions with RFC2217

Code of Conduct

Yes, I agree

CANDIDATE · ISSUE

Unable to print unicode characters when running repl with mpremote

openby XuanTongYaoopened 2024-06-08updated 2026-01-10

bugtoolsunicode

Port, board and/or hardware

RP2 Pico

MicroPython version

MicroPython v1.22.1 on 2024-01-05; Raspberry Pi Pico with RP2040

Reproduction

Create a file called tt.py
Write the following contents

print("你好")

Run this command in the same directory:mpremote mount .
import tt

Expected behaviour

Expected to print "你好".

Observed behaviour

PS D:\PROJECTS\Github\MicroPython-uFont> mpremote mount .
Local directory . is mounted at /remote
Connected to MicroPython at COM6
Use Ctrl-] or Ctrl-x to exit this shell
>
MicroPython v1.22.1 on 2024-01-05; Raspberry Pi Pico with RP2040
Type "help()" for more information.
>>> import tt
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "C:\Users\YHW\AppData\Local\Programs\Python\Python312\Scripts\mpremote.exe\__main__.py", line 7, in <module>
  File "C:\Users\YHW\AppData\Local\Programs\Python\Python312\Lib\site-packages\mpremote\main.py", line 536, in main
    do_repl(state, argparse_repl().parse_args([]))
  File "C:\Users\YHW\AppData\Local\Programs\Python\Python312\Lib\site-packages\mpremote\repl.py", line 89, in do_repl
    do_repl_main_loop(
  File "C:\Users\YHW\AppData\Local\Programs\Python\Python312\Lib\site-packages\mpremote\repl.py", line 54, in do_repl_main_loop  
    console_out_write(console_data_out)
  File "C:\Users\YHW\AppData\Local\Programs\Python\Python312\Lib\site-packages\mpremote\repl.py", line 83, in console_out_write  
    console.write(b)
  File "C:\Users\YHW\AppData\Local\Programs\Python\Python312\Lib\site-packages\mpremote\console.py", line 119, in write
    buf = buf.decode() if isinstance(buf, bytes) else buf
          ^^^^^^^^^^^^
UnicodeDecodeError: 'utf-8' codec can't decode bytes in position 0-1: unexpected end of data

Additional Information

Obviously this error occurs on the PC, so I guess there must be something wrong with the mpremote source code. The error is also triggered when printing other unicode characters, such as Japanese, emoji, etc.

As far as I know, many people use mpremote mount . to quickly demo their code, and I'd like to, but something went wrong.

Is there any way to avoid this problem?
I could convert unicode characters to hexadecimal and print them, but that's pointless.
Printing unicode characters works perfectly fine with tools like thonny.

Code of Conduct

Yes, I agree

mpremote REPL and mount issues with socket:// and RFC2217 connections

Port, board and/or hardware

MicroPython version

Reproduction

1 unable to mount host filesystem over socket connections

2 Incorrect newline handling in interactive repl over socket

3 repl over socket://

4 repl over rfc2217

Expected behaviour

Observed behaviour

Additional Information

Code of Conduct

Unable to print unicode characters when running repl with mpremote

Port, board and/or hardware

MicroPython version

Reproduction

Expected behaviour

Observed behaviour

Additional Information

Code of Conduct

Keyboard