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SlawekN
Associate
April 24, 2026
Solved

ST67W611M1 UDP client socket blocked (mission_t01)

  • April 24, 2026
  • 1 reply
  • 135 views

Hi,

while integrating the module, we noticed that UDP client connections appear to be explicitly blocked in the driver (w61_at_net.c) for mission_t01 firmware (LwIP offload). The following code only allows TCP and SSL connections:

if ((conn->Protocol != W61_NET_TCP_CONNECTION) && (conn->Protocol != W61_NET_TCP_SSL_CONNECTION)
#if (W61_NET_IPV6_ENABLE == 1)
&& (conn->Protocol != W61_NET_TCPV6_CONNECTION) && (conn->Protocol != W61_NET_TCPV6_SSL_CONNECTION)
#endif /* W61_NET_IPV6_ENABLE */
)
{
NET_LOG_ERROR("Only TCP and SSL protocols are supported for client connections\n");
return W61_STATUS_ERROR;
}

However, according to the official AT command documentation, UDP client connections are supported:
https://applist67.github.io/Web_AT_Documentation_ST67/v2.0.106/index.html#establish-udp-connection

After commenting out this restriction, I was able to establish a UDP client connection successfully, and communication seems to work.

Is there a specific reason why UDP client sockets are blocked at this level?
Are there any known limitations or risks when enabling UDP this way?

Thanks in advance for your clarification.

    Best answer by Louis AUDOLY

    Hello @SlawekN ,

    The UDP sockets are available on the middleware. You have to create a new UDP socket and then call the 

    W61_Net_SendData_Non_Connected() function as you are working in UDP.
    This is enough to have a UDP client connection.
     
    This is also possible to do the way you are pointing, but this is a choice of implementation we have done in our code, so you may encounter unexpected behavior doing this way.
    We keep the function W61_Net_StartClientConnection() for connected types, TCP (v4/v6) and SSL.
    For unconnected connections you can directly use the API function W6X_Net_Sendto() to exchange data once your socket is created
     
    Hopping this answer your question.
    Regards
    Louis
     

    1 reply

    Louis AUDOLY
    Louis AUDOLYAnswer
    ST Employee
    April 28, 2026

    Hello @SlawekN ,

    The UDP sockets are available on the middleware. You have to create a new UDP socket and then call the 

    W61_Net_SendData_Non_Connected() function as you are working in UDP.
    This is enough to have a UDP client connection.
     
    This is also possible to do the way you are pointing, but this is a choice of implementation we have done in our code, so you may encounter unexpected behavior doing this way.
    We keep the function W61_Net_StartClientConnection() for connected types, TCP (v4/v6) and SSL.
    For unconnected connections you can directly use the API function W6X_Net_Sendto() to exchange data once your socket is created
     
    Hopping this answer your question.
    Regards
    Louis
     
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