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#78920
30.1; Process sentinel is not called when DNS lookup fails
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Message #11 received at 78920 <at> debbugs.gnu.org (full text, mbox):
On 6/29/25 1:13 AM, Eli Zaretskii wrote:
>> Date: Sat, 28 Jun 2025 18:04:07 -0400
>> From: Shawn Henson <shawn <at> shenso.name>
>>
>> I was testing a function of mine which wraps `url-retrieve', and I found
>> myself confused that my callback was not being reached with bad
>> host names, and upon debugging discovered the process sentinel was not
>> being called at all. Using the Lisp debugger added further confusion
>> because the process status of the returned buffer would be "failed", but
>> this was not the case during normal evaluation due to race conditions.
>>
>> You can reproduce this with make-network-process:
>>
>> ```
>> (let ((my-test-proc (make-network-process :name "dns-fail-test"
>> :buffer "dns-fail-test-buf"
>> :host "thisisnotarealhostname"
>> :service 80
>> :nowait t
>> :sentinel (lambda (process event)
>> (print event)))))
>> (message "process status: %s" (process-status my-test-proc)))
>> ```
>>
>> After evaluation, the *Messages* buffer includes:
>>
>> ```
>> process status: connect
>> ```
> What happens if you use ':nowait nil' instead? Is the sentinel get
> called?
In this case, an error is signaled upon evaluating the function:
```
Debugger entered--Lisp error: (error "thisisnotarealhostname/80 Name or
service not known")
make-network-process(:name "dns-fail-test" :buffer
"dns-fail-test-buf" :host "thisisnotarealhostname" :service 80 :nowait
nil :sentinel #f(lambda (process event) [t] (print event)))
```
This seems in line with the function documentation, which seems to
confirm the sentinel should be
called when it is 't', which is the case for `url-retrieve'.
```
:nowait BOOL -- If NOWAIT is non-nil for a stream type client
process, return without waiting for the connection to complete;
instead, the sentinel function will be called with second arg matching
"open" (if successful) or "failed" when the connect completes.
Default is to use a blocking connect (i.e. wait) for stream type
connections.
```
This bug report was last modified 5 days ago.
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