AWS SNSClient publish call could not reach endpoint - c++

Question

I am trying to publish a message to a topic using the AWS SNSClient from the c++ SDK.
Can someone help me to find a way to figure out what is wrong with my approach? The error message I am getting only says that the "endpoint could not be reached".
I am trying to figure out where my request hangs - in my point of view it could be one of the following:
the docker container the c++ app is running in is blocking the requests somehow (new to docker)
the client configuration is wrong (region, arn, creditials wrong?)
the request is malformed (some parameters not set? Message type maybe?)
Does someone know how I can debug my request and see what the issue is?
Thanks! My code looks something like this (api init and shutdown is omitted):
Aws::SNS::SNSClient client(credentials , config);
Aws::SNS::Model::PublishRequest pubReq;
pubReq.SetTopicArn("...");
pubReq.SetMessage("Test message");
pubOutcome = client.Publish(pubReq);
if(! pubOutcome.IsSuccess() ){
std::cout << "outcome: " << pubOutcome.GetError().GetMessage() << std::endl;
}

Answer 1

My guess without being able to see your code is that you have not specified the correct region. If your code hangs for a few seconds then this is most likely the problem.
Add a line of code like this before your create the SNS Client:
config.region = "us-west-2";
To enable debugging add this line before Aws::InitAPI(options)
options.loggingOptions.logLevel = Aws::Utils::Logging::LogLevel::Debug;
The headers for logging:
#include <aws/core/utils/logging/DefaultLogSystem.h>
#include <aws/core/utils/logging/AWSLogging.h>
Then you can review the logfile that is generated. It will start with "aws_sdk"
I use Visual Studio, so I prefer to step into the code to figure out what is wrong. Sometimes it is simpler to review the logfile.