UKTidalEvents Plugin

[Rasbats]

UKHO has published an open API that enables developers to retrieve HW/LW times for 600 tidal stations around the UK.

https://www.admiralty.co.uk/digital-...s/uk-tidal-api

I have been able to download all the GeoJSON files via MS Internet Explorer but Firefox shows errors for the tidal events and stations download.

Using 'OCPN_downloadFile' from the OpenCPN API caused the downloads to fail. Does the function work with an 'https' url? Can the appropriate headers be sent? When Curl (with SSL enabled) was used it was necessary to treat the URL as insecure.

I would like to keep all the code within the plugin. If necessary the Curl program could be included, but then Windows only. Trying to avoid libCurl to keep things simple.

If anyone can point me to a solution for using 'OCPN_downloadFile' with the UKHO API it would be much appreciated.

Mike

[bdbcat]

Mike...

Show us some code snippets, and results.

Dave

[did-g]

Originally Posted by Rasbats

UKHO has published an open API that enables developers to retrieve HW/LW times for 600 tidal stations around the UK.

https://www.admiralty.co.uk/digital-...s/uk-tidal-api

Using 'OCPN_downloadFile' from the OpenCPN API caused the downloads to fail. Does the function work with an 'https' url? Can the appropriate headers be sent? When Curl (with SSL enabled) was used it was necessary to treat the URL as insecure.

Mike

It does https but some servers may not always work with curl linked against gnutls, which curl version or opencpn are you using?


For testing mitmproxy can help a lot.


Didier

[Rasbats]

Originally Posted by did-g

It does https but some servers may not always work with curl linked against gnutls, which curl version or opencpn are you using?

Curl binary with SSL came from here:
cURL groks URLs - CURL 7.61.0
OpenCPN at V 4.8.4, API 1.13

Show us some code snippets, and results.

================================================
wxString s = _T("/");
wxString defaultDir = *GetpSharedDataLocation() + _T("plugins")
+ s + _T("uktidalevents_pi") + s + _T("data") + s;

wxString stations = _T("json.txt");

wxString fn = defaultDir + stations;
wxFile f(fn);

wxString urlString = _T("https://admiraltyapi.azure-api.net/uktidalapi/api/V1/Stations/0014/TidalEvents?key=80d84068452d4f58ad1b9dcf9cacf18c") ;
wxURI url(urlString);

_OCPN_DLStatus ret = OCPN_downloadFile(url.BuildURI(), fn,
_T("UKTidalEvents"), _T("")
, wxNullBitmap, this,
OCPN_DLDS_ELAPSED_TIME | OCPN_DLDS_ESTIMATED_TIME | OCPN_DLDS_REMAINING_TIME | OCPN_DLDS_SPEED | OCPN_DLDS_SIZE | OCPN_DLDS_CAN_PAUSE | OCPN_DLDS_CAN_ABORT,
20);

if (ret == OCPN_DL_FAILED){
wxMessageBox(_("Download failed"));
wxRemoveFile(fn);
return;
}
else if (ret == OCPN_DL_NO_ERROR) {
wxMessageBox(_("Success"));
return;
}
================================================
The URL works with CTRL+Click in VS2013.

Thanks
Mike

[bdbcat]

Mike...

Code is clear enough.
Have you tried to trace the execution of the API call? Exactly why does it return "OCPN_DL_FAILED"?

Dave

[did-g]

There's something with the server but I don't have time below one is working one is returning an error from the server.

2018-08-07 10:45:29 GET https:// ...
<- 500 Internal Server Error text/html 3.34k 100ms
Request Response Detail
Server Connection:
Address admiraltyapi.azure-api.net:443
Resolved Address 51.141.89.70:443
HTTP Version HTTP/1.1
ALPN http/1.1
Server Certificate:
Type RSA, 2048 bits
SHA1 digest CB:33:E9:27:A7:6A:CB:77:C8:21:5A:AF:4F:98:A3:FF:78 :13:90:69
Valid to 2020-01-11 18:29:16
Valid from 2018-01-11 18:29:16
Serial 490616592448058144929574954273345938441409796
Subject CN *.azure-api.net
Issuer C US
ST Washington
L Redmond
O Microsoft Corporation
OU Microsoft IT
CN Microsoft IT TLS CA 4
Alt names *.azure-api.net, *.portal.azure-api.net, *.management.azure-api.net, *.scm.azure-api.net, *.configuration.azure-api.net,
*.regional.azure-api.net
Client Connection:
Address ::ffff:10.8.0.21:38555
HTTP Version HTTP/1.1
TLS Version TLSv1.2
Server Name Indication admiraltyapi.azure-api.net
Cipher Name ECDHE-RSA-AES128-GCM-SHA256
ALPN http/1.1
Timing:



Request:


Host: admiraltyapi.azure-api.net
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:61.0) Gecko/20100101 Firefox/61.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: fr,en-US;q=0.7,en;q=0.3
Accept-Encoding: gzip, deflate, br
DNT: 1
Connection: keep-alive
Upgrade-Insecure-Requests: 1
Cache-Control: max-age=0

2018-08-07 10:56:23 GET https:// ...
<- 200 OK application/json 4.15k 337ms
Request Response Detail
Server Connection:
Address admiraltyapi.azure-api.net:443
Resolved Address 51.141.89.70:443
HTTP Version HTTP/1.1
Server Certificate:
Type RSA, 2048 bits
SHA1 digest CB:33:E9:27:A7:6A:CB:77:C8:21:5A:AF:4F:98:A3:FF:78 :13:90:69
Valid to 2020-01-11 18:29:16
Valid from 2018-01-11 18:29:16
Serial 490616592448058144929574954273345938441409796
Subject CN *.azure-api.net
Issuer C US
ST Washington
L Redmond
O Microsoft Corporation
OU Microsoft IT
CN Microsoft IT TLS CA 4
Alt names *.azure-api.net, *.portal.azure-api.net, *.management.azure-api.net, *.scm.azure-api.net, *.configuration.azure-api.net,
*.regional.azure-api.net
Client Connection:
Address ::ffff:10.8.0.21:38565
HTTP Version HTTP/1.1
TLS Version TLSv1.2
Server Name Indication admiraltyapi.azure-api.net
Cipher Name ECDHE-RSA-AES128-GCM-SHA256
Timing:
Client conn. established 2018-08-07 10:56:22.784
Client conn. TLS handshake 2018-08-07 10:56:23.049



Request
User-Agent: curl/7.35.0
Host: admiraltyapi.azure-api.net
Accept: */*
Accept-Encoding: deflate, gzip

Finding what trigger the server error shouldn't be too hard.

[Rasbats]

Thanks Didier. This sort of stuff is beyond me.

This came back when using Curl + SSL without the -k option:

C:\plugins\admiralty>curl -o "c:/plugins/admiralty/output.txt" -X GET "https:
//admiraltyapi.azure-api.net/uktidalapi/api/V1/Stations/0014/TidalEvents?duratio
n=1&key=80d84068452d4f58ad1b9dcf9cacf18c"
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: https://curl.haxx.se/docs/sslcerts.html

curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.

Is there any way of forcing an insecure request?
Mike

[did-g]

Originally Posted by Rasbats

Thanks Didier. This sort of stuff is beyond me.

This came back when using Curl + SSL without the -k option:

Is there any way of forcing an insecure request?
Mike

Yes there's, but is it a good idea? Updating certificates list is likely a better solution.

Anyway issue seems to be

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8



ie server doesn't like:


wget -v --debug --header='Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8' ...

which BTW is a sample coming from https://developer.mozilla.org/en-US/...Headers/Accept


it's set in src/wxcurl/base.cp, IMO should be 'Accept: */*'

[bdbcat]

Mike...

I had some trouble with this also in ofc_pi. Not the same, but similar.

Ended up deriving a class from curl, so that I had finer control. Take a look at ofc_pi source:
https://github.com/bdbcat/ofc_pi


Look in ofcShop.cpp:

class wxCurlHTTPNoZIP : public wxCurlHTTP

Dave

[rgleason]

Mike, I am curious, would this data be able to populate the Admiralty Tides pi which requires manual input at this point? --On the other hand, perhaps you have something else in mind like OTcurrent?

[Rasbats]

Rick ...

Admiralty Tides pi requires hard copy UKHO tide tables. Everything off-line. Predictions only limited by the annual edition of the tide tables.

UKTidalEvents - if I can crack the server problem - works on-line. Predicts HW/LW for up to seven days in the future. No tidal current predictions from the API. It is the number of tidal stations that can be accessed easily that is the main attraction.

Mike

[Rasbats]

Thanks for the help, but it is not worth spending any more time on this at the moment.

The same data is available online e.g.:
https://www.tidetimes.org.uk/cotehele-quay-tide-times

Mike

[OlleH]

Hi, is it possible to save the file downloaded for UK Tides plugin? If I am crossing the North Sea from Norway I will download Tides for 7 days and I might not want all waypoints active for three days during passage. Only choise I see as it is today is to turn of wapoints and rutes, but I still want my rutes visible on such a trip.

[Rasbats]

Sorry, the tidal station waypoints are only active when you have an Internet connection. In the middle of the North Sea they will not be needed. They will not be there when OpenCPN is re-opened and the plugin has not been started.

UK Hydrographic Office does not allow the data to be saved by the plugin. Nothing would stop the user taking a screenshot of a set of tide predictions for future reference.

Mike

p.s. Thanks, I found a bug. If you leave the predictions screen open and close OpenCPN you will get a crash. Easy to fix!

[OlleH]

Thanks for your answer Rasbats. The reason was not to use it on the North sea. It was to have it avaliable when arriving coast of Scottland. Is it possible to make a funktion to save a pdf-file instead of a screen shot?
/Olleh