Trouble connecting/downloading packages

erik_l | Posts: 6

Trouble connecting/downloading packages

Friday, September 6, 2019 at 12:24pm

I've been having a bit of trouble connecting to the Canadian sandbox environment. The specific error message I'm getting is: "Could not get package. Exception: Object reference not set to an instance of an object." Here's the code (irrelevant bits stripped out):

Dim _eslClient As New EslClient("Our API Key goes here", "https://sandbox.e-signlive.ca/api")

Dim docPackage As DocumentPackage
Dim pkgId As New PackageId("Package ID Goes Here")

docPackage = _eslClient.GetPackage(pkgId)

And that's when it throws a System.Net.Sockets.SocketException and we get the error code. For the record, I've also tried

_eslClient.SystemService.GetApplicationVersion()

without any success. That one also threw a socket exception and gave a similar error message. This is .NET Framework 4.8 (we recently upgraded). The package IDs are coming straight from the callback and we've verified the API key is correct, so I'm at a little bit of a loss. The version of Silanis.ESL.dll is 11.0.1.0 and the Runetime Version is v2.0.50727. Any thoughts?

September 6 Created

January 21 Last Updated

6 years ago Last Reply

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Answered by Duo_Liang

Approved Answer

Duo_Liang | Posts: 3777

Reply to: Trouble connecting/downloading packages

Wednesday, September 11, 2019 at 10:51am

Hi erik, This error sounds like a TLS issue, have you tried to specify TLS version using below code:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

Just put this code before you built the HttpClient object. Duo

erik_l | Posts: 6

Reply to: Trouble connecting/downloading packages

Friday, September 6, 2019 at 12:55pm

Oh, if it helps, this is what I'm getting in the Visual Studio output window:

Exception thrown: 'System.Net.Sockets.SocketException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.ObjectDisposedException' in System.dll
Exception thrown: 'System.Net.Sockets.SocketException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.IO.IOException' in System.dll
Exception thrown: 'System.ObjectDisposedException' in System.dll
Exception thrown: 'System.Net.WebException' in System.dll
Exception thrown: 'System.Net.WebException' in System.dll
Exception thrown: 'System.NullReferenceException' in Silanis.ESL.dll
Exception thrown: 'Silanis.ESL.SDK.EslException' in Silanis.ESL.dll

And if it matters we're on Newtonsoft.Json v12.0.2

Duo_Liang | Posts: 3777

Reply to: Trouble connecting/downloading packages

Friday, September 6, 2019 at 01:29pm

Hi there, Just a few questions first, are you connecting through a proxy? Can you connect to OSS through RESTful API? And furthermore, can you access other HTTPS resources on your server? For Test with OSS connection:

HTTP Request
POST /api/sysinfo

HTTP Headers
Accept: application/json
Content-Type: application/json
Authorization: Basic api_key

For Test with other HTTPS resources, you can try make a GET to retrieve my github repo:

HTTP Request
GET https://api.github.com/users/liangduo1993/repos

HTTP Headers
Accept, "application/json"
User-Agent, "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36"

Duo

erik_l | Posts: 6

Reply to: Trouble connecting/downloading packages

Monday, September 9, 2019 at 05:42am

So I've verified it's working when I access the RESTful API directly (it gives 405 Method Not Allowed when I tried /api/sysinfo on the Canadian sandbox, but /api/callback gave the expected result) and for grins I tried the GitHub repo and that worked too, so I suspect you might be right and there's an issue in the corporate network firewall. I'll ask around and see if that resolves it.

erik_l | Posts: 6

Reply to: Trouble connecting/downloading packages

Monday, September 9, 2019 at 07:13am

I've been told it isn't the firewall, so I tried out something a little bit different. Since accessing the API directly worked in Postman, I figured I'd try it programmatically.

    Public Function TestESignConnection() As String Implements IESLDownloaderSVC.TestESignConnection
        Dim response As HttpResponseMessage
        Try
            _httpClient.DefaultRequestHeaders.Authorization = New AuthenticationHeaderValue("Authorization", "Basic ")
            _httpClient.DefaultRequestHeaders.Accept.Add(New MediaTypeWithQualityHeaderValue("application/json"))

            response = _httpClient.GetAsync("https://sandbox.e-signlive.ca/api/callback").Result
            Return JsonConvert.SerializeObject(response)
        Catch ex As Exception
            Return ex.ToString
        End Try
    End Function

This gave the same result as the SDK:

"System.AggregateException: One or more errors occurred. ---> System.Net.Http.Http" +
    "RequestException: An error occurred while sending the request. ---> System.Net.W" +
    "ebException: The underlying connection was closed: An unexpected error occurred " +
    "on a send. ---> System.IO.IOException: Unable to read data from the transport co" +
    "nnection: An existing connection was forcibly closed by the remote host. ---> Sy" +
    "stem.Net.Sockets.SocketException: An existing connection was forcibly closed by " +
    "the remote host\r\n etc. etc.

So I'm honestly at a little bit of a loss here. It sort of seems like the problem is the app itself, although I hasten to add it's working fine in production. I'll keep checking with our network people, but for the record, could you maybe let me know what problems with a proxy I should be asking about?

Duo_Liang | Posts: 3777

Reply to: Trouble connecting/downloading packages

Monday, September 9, 2019 at 07:16am

Hi erik, Can I know whether your calls went through a proxy server? For applications integrated with .Net SDK, normally you don't need to specify proxy information because .Net by default will use the system default proxy. But you can always explicitly assign the proxy information as mentioned in this guide:

ProxyConfiguration httpProxyConfiguration = ProxyConfigurationBuilder.newProxyConfiguration()
                .WithHttpHost("serverAddress") //e.g. localhost
                .WithHttpPort(portNumber) //e.g. 8001
                .Build();
Boolean allowAllSSLCertificates = false;		
EslClient client = new EslClient(API_KEY, API_URL, allowAllSSLCertificates, httpProxyConfiguration);

The guide also covers the solution for RESTful calls using HttpClient. Duo

erik_l | Posts: 6

Reply to: Trouble connecting/downloading packages

Wednesday, September 11, 2019 at 09:02am

I've just been told, it's not being routed through a proxy server. More mysteriously the RESTful API calls aren't giving us socket exceptions when we run them in a different project, but in the normal place it's giving us that "Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host." If this isn't something you're familiar with/have had customers run into before, then I guess I'll just have to keep messing around with it.

erik_l | Posts: 6

Reply to: Trouble connecting/downloading packages

Wednesday, September 11, 2019 at 11:51am

That totally worked. For use with the SDK I assume it should just go before we build the client object, correct? Like so:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
_eslClient = New EslClient(ESLAPIKey, ESLServiceURL)

Duo_Liang | Posts: 3777

Reply to: Trouble connecting/downloading packages

Wednesday, September 11, 2019 at 02:09pm

Great to hear that! Yes, this code also works for the SDK. Tell us if it doesn't work as expected! Duo