Hi!
I've run strace on the deivce, and I got:
setsockopt(3, SOL_TCP, TCP_KEEPINTVL, [15], 4) = 0
So the device process sets the TCP keep alive to 15 sec.
Lajos Rancz a következőt írta (2022. március 28., hétfő, 10:40:33 UTC+2):
> Hi all,
>
> I'm developing an IoT application, both the server (runs on a Digital
> Ocean droplet) and the client device application (runs on an embedded
> Linux) are written in Go. The internet connection between the devices and
> the server is provided by LTE Cat M1.
> The application requires a live connection between the device and the
> server (because of real-time events), so I use server-side streaming:
> message DeviceWatchRequest {
> int32 token = 1;
> }
>
> message DeviceWatchResponse {
> int64 id = 1;
> uint32 type = 2;
> bytes data = 3;
> }
>
> service DeviceService {
> ...
> rpc Watch(DeviceWatchRequest) returns (stream DeviceWatchResponse);
> }
>
> The whole system works well, BUT the data usage is unacceptably huge, I
> send only a few bytes (DeviceWatchResponse.data) hourly. So, I've dumped
> the TCP traffic with the tcpdump utility.
> What I see is that the vast majority of data usage is due to TCP keepalive:
>
> [image: wireshark.png]
>
> So, a keep-alive operation consists of 4 packets, all four are 68 bytes
> long; eg. one keep-alive operation is 272 bytes long. There are 86400
> seconds in a day, so 86400/15 = 5760 keep-alive operations are done in a
> day; it means 5760*272 = 1 566 720 bytes ~ 1.5 MB/day!
> My whole monthly data usage could be that much, not my daily. As
> https://www.emnify.com/pricing: 1 MB/month is around 1 EUR/month/device,
> 50 MB is 2.65 EUR/month/device.
> So, I've tried to set the keep-alive options on client side:
> conn, err := grpc.Dial(*addr, grpc.WithInsecure(),
> grpc.WithKeepaliveParams(keepalive.ClientParameters{Time: 60 * time.Second,
> Timeout: 5 * time.Second, PermitWithoutStream: true}))
> But after 3 minutes the connection is dropped. The keep-alive
> documentation (https://github.com/grpc/grpc/blob/master/doc/keepalive.md
> and https://pkg.go.dev/google.golang.org/grpc/keepalive) is contradictory.
>
> What can I do?
>
> Regards,
> Lajos
>
>
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