Dart: client.post() method in the http.dart package is hanging and isn't returning a future - http

Question

I am currently implementing a simple ONVIF client program in dart and am having a bit of trouble with handling futures in the http.dart package.
In my code below, the client.post() method returns a Future<response> (containing body/header/status code and so on...) and in my case I would need to receive this before the if/else statement, hence why I have used await. Trouble is the program just hangs and doesn't proceed past the client.post()line.
I know I might need to do a client.close() somewhere but I've tried lots of different ways and nothing works. Here is my current code with some comments to try and explain it a bit:
// The Variables:
// reqSysDateAndTime is a soap message we are sending to the device.
// onvifDev is just a place where the device details are stored.
// probeMatch is a class that stores important info from the ws-discovery stage.
Future<String> checkXaddrsAndGetTime(Device onvifDev, ProbeMatch probeMatch) async {
// Set up the client and uri.
Uri uri = Uri.parse(probeMatch.xaddrs);
http.Client client = http.Client();
// Send the POST request, with full SOAP envelope as the request body
print('[Setup]: Listening for Date/Time response...');
Response response = await client.post(uri, body: reqSysDateAndTime);
print("${response.body}");
// Determine if the address is usable or not.
if (response != null) {
// Set this address as 'working'
onvifDev.xAddrs = probeMatch.xaddrs;
return response.body;
}
else {
return null; // The address does not work
}
}
I also know that this isn't an issue with the actual body of the request because if I do...
client.post(uri, body: reqSysDateAndTime).then((onValue) => print(onValue.body));
...instead, it will print out the response which I'm expecting.
I understand that this is probably a small fix that I'm missing but any help would be much appreciated.
Cheers.

Answer 1

To briefly answer my own question, turns out it was a silly error on my part where the address I was using was link-local - hence why it was hanging at client.post(). There is a nice method in the InternetAddress class here, amongst some other useful methods, which checks to see if the address is link-local or not.