allow user pass ping_data in connection

[liuyangc3]

No description provided.

[aaugustin]

You didn't explain why you're proposing this, making it hard for me to tell if it's the right solution.

Technically, your code will break if ping_timeout is None and you don't receive a pong within ping_interval.

[aaugustin]

The next step would be for me to understand what is the purpose of this feature and to decide whether I want to support it in the library.

[aaugustin]

You may be proposing this because some servers require clients to send a ping with a specific content at a minimum frequency. However, most of those servers expect it in a Text frame, not a Ping frame. With the proposed ping_data API, users are likely to get confused.

Servers relying on protocol-level ping/pong in Ping/Pong frames, as opposed to application-level ping/pong in Text frames, usually don't care about the content of pings and pongs. websockets has been sending random 4-bytes payloads in pings for a decade without issues.

[liuyangc3]

Hi @aaugustin In some backend implement, server doesn't response the ping when the ping data is not a str type, which cause a pong timeout and connection close exception on client side. new TCP connection is recreated after each ping interval.

The ping data in keep_alive imeplement is forced to random bytes. In my case, I tried to hardcode self.ping("") and connection is back to normal.

The the protocal desgin itself provides ability to custom the ping data in send_ping() method, but the current high-level imeplement, which lose the ability, that's why this PR proposing for.

[liuyangc3]

You may be proposing this because some servers require clients to send a ping with a specific content at a minimum frequency. However, most of those servers expect it in a Text frame, not a Ping frame. With the proposed ping_data API, users are likely to get confused.

Servers relying on protocol-level ping/pong in Ping/Pong frames, as opposed to application-level ping/pong in Text frames, usually don't care about the content of pings and pongs. websockets has been sending random 4-bytes payloads in pings for a decade without issues.

Yeah, but random 4-bytes payloads not suite for all caces, we just need a way to allow user control the keep alive behaviour, maybe there's better proposal

[aaugustin]

some backend implement, server doesn't response the ping when the ping data is not a str type, which cause a pong timeout

I guess "not a str type" means "not valid UTF-8"; this is a clear spec violation as explained here: #922 (comment); those servers are buggy and need to be fixed.

Alternatively, you can disable pings with ping_interval=None.

I'm not going to complexify the API because "some backend implement" is buggy. The API has a lot of parameters already; I'm not adding new ones without a very strong reason.

If I wanted to make a change, I'd send a random ASCII string rather than random bytes. Until now, getting buggy servers to fix their bugs has worked for me :-)