Failed to bind to port 61234

Andrew Neil · ‎2025-04-01

So I'd been merrily using STM32CubeIDE all morning, doing the usual code-download-debug cycle with no problems at all.

Then, after some code updates & successful build, it suddenly can't reach the GDB server:

STMicroelectronics ST-LINK GDB server. Version 7.4.0
Copyright (c) 2023, STMicroelectronics. All rights reserved.
Starting server with the following options:
   Persistent Mode : Disabled
   Logging Level : 1
   Listen Port Number : 61234
   Status Refresh Delay : 15s
   Verbose Mode : Disabled
   SWD Debug : Enabled
   InitWhile : Enabled

Failed to bind to port 61234, error code -1: No error
Failure starting GDB server: TCP port 61234 not available.
Shutting down...
Exit.

Several people seem to have had this recently; eg,

https://community.st.com/t5/stm32cubeide-mcus/cubeide-1-18-cannot-detect-st-link-anymore/m-p/784313?search-action-id=49992011530&search-result-uid=784313

https://community.st.com/t5/stm32cubeide-mcus/st-link-error-failed-to-bind-to-port-61235-failure-starting-swv/m-p/784642?search-action-id=49992011530&search-result-uid=784642

So why should this change when nothing has been updated - I'm just working in the IDE as usual ?!

This is CubeIDE v1.13.0 - so old, yes - but surely no reason for it to just give up in the middle of a session?

On Windows-11 - no updates have happened.

Andrew Neil · ‎2025-04-01

Restarting the IDE made no difference.

Restarting the PC restored operation.

Would still like to know why the sudden failure to bind to the port ?

Pavel A. · ‎2025-04-01

The same old question: is any antivirus (or VPN, or corporate brain-***ing-ware) installed?

AFAIK these ports are not reserved in Windows in any way. So other apps or Windows components can steal them.

Update: The helpful AI informs that user can define several ranges of ports to exclude from automatic allocation - but this won't prevent other apps to use these ports explicitly. The command is netsh int ipv4 add excludedportrange protocol=tcp startport=<port_number> numberofports=<N>

Andrew Neil · ‎2025-04-01

@Pavel A. wrote:
The same old question: is any antivirus (or VPN, or corporate brain-***ing-ware) installed?

Just the standard Windows Defender.

But why would it suddenly start blocking this port - and stop blocking it after a reset?

The firewall exceptions are already set up - otherwise it wouldn't have been working for all these years.

@Pavel A. wrote:
So other apps or Windows components can steal them.

Again, what would suddenly steal it - and stop after a reset?

Why has it not happened before?

What can be done to see if it's a problem with GDB itself, or with some thing(s) else "blocking" or "stealing" GDB's port?

Pavel A. · ‎2025-04-01

Have you tried to change the port - after checking the active busy and reserved ports, disable Windows firewall?

To check busy ports: netstat -ano

To check reserved ports: netsh int ipv4 show excludedportrange tcp active , netsh int ipv4 show excludedportrange udp active

Andrew Neil · ‎2025-04-02

@Pavel A. wrote:
Have you tried to change the port

Here?

@Pavel A. wrote:
after checking the active busy and reserved ports

Microsoft Windows [Version 10.0.26100.3476]
(c) Microsoft Corporation. All rights reserved.

>netstat -ano

Active Connections

  Proto  Local Address          Foreign Address        State           PID
  :
  TCP    0.0.0.0:61234          0.0.0.0:0              LISTENING       356
  TCP    0.0.0.0:61235          0.0.0.0:0              LISTENING       356
  :
  TCP    127.0.0.1:60275        127.0.0.1:61234        ESTABLISHED     12276
  TCP    127.0.0.1:60277        127.0.0.1:61234        ESTABLISHED     4548
  TCP    127.0.0.1:61234        127.0.0.1:60275        ESTABLISHED     356
  TCP    127.0.0.1:61234        127.0.0.1:60277        ESTABLISHED     356
  :

>netsh int ipv4 show excludedportrange tcp active

Protocol tcp Port Exclusion Ranges

Start Port    End Port
----------    --------
     49692       49791
     49892       49991
     50000       50059     *
     50060       50159
     50160       50259
     50260       50359
     61893       61992
     63720       63819

* - Administered port exclusions.


>netsh int ipv4 show excludedportrange udp active

Protocol udp Port Exclusion Ranges

Start Port    End Port
----------    --------
     50000       50059     *
     63654       63753
     63854       63953
     63954       64053
     64054       64153
     64154       64253
     64694       64793
     65015       65114

* - Administered port exclusions.

>

But, again, it's all back to working now - and had been for several years. Why would it just change?

I shall have to try to remember this thread if it happens again ...