Re: [lwip-users] netconn_connect returns OK when connection refused?

[Grant Edwards]

On 2022-01-20, Grant Edwards <grant.b.edwards@gmail.com> wrote:

> I'm running into a problem where netconn_connect always returns OK
> immediately, even when the connection was refused by the server (it
> replies to the SYN with a RST). Subsequent attempts to write to the
> connection return -14 (ERR_RST) or -11 (ERR_CONN).

> Shouldn't netconn_connect() return an error if the connection was
> refused?  If the server accepts the conneciton, it seems to work OK.
>
> Here's the relevent code:
>
>
>       conn = netconn_new(NETCONN_TCP);
>       if (!conn)
>         {
>           printf("conn NULL\n");
>           return;
>         }
>       e = netconn_connect(conn, &ip, 7000);
>       if (e != ERR_OK)
>         {
>           printf("%s[%d] netconn_connect e=%d\n",__func__,exinf,e);
>           netconn_delete(conn);
>           return;
>         }
>       printf("connected\n");
>       ...
>           e = netconn_write_partly(conn, data, dsize, NETCONN_COPY, &written);
>           if (e != ERR_OK)
>             printf("%s[%d] netconn_write e=%d\n",__func__,exinf,e);

I'm still stumped by this. It's 100% reliable: netconn_connect()
returns ERR_OK even though the server responded to the SYN
with a RST. Subsequent writes to that connection fail.

I get the same resutls using the socket api. The call to connect()
returns 0, but then send() fails.

Nobody else has seen this?