Define service endpoint address for WsCreateServiceHost - web-services

Question

I'm plying with HttpCalculatorServiceExample located in MSDN. What endpoint address should be defined in WS_SERVICE_ENDPOINT structure. Expression L"http://+:80/example" looks strange for me. What +:80 means? I suppose 80 is port number. But why +?
int __cdecl wmain(int argc, __in_ecount(argc) wchar_t **argv)
{
UNREFERENCED_PARAMETER(argc);
UNREFERENCED_PARAMETER(argv);
HRESULT hr = NOERROR;
WS_SERVICE_HOST* host = NULL;
WS_SERVICE_ENDPOINT serviceEndpoint = {};
const WS_SERVICE_ENDPOINT* serviceEndpoints[1];
serviceEndpoints[0] = &serviceEndpoint;
WS_ERROR* error = NULL;
WS_SERVICE_ENDPOINT_PROPERTY serviceEndpointProperties[1];
WS_SERVICE_PROPERTY_CLOSE_CALLBACK closeCallbackProperty = {CloseChannelCallback};
serviceEndpointProperties[0].id = WS_SERVICE_ENDPOINT_PROPERTY_CLOSE_CHANNEL_CALLBACK;
serviceEndpointProperties[0].value = &closeCallbackProperty;
serviceEndpointProperties[0].valueSize = sizeof(closeCallbackProperty);
// Initialize service endpoint
serviceEndpoint.address.url.chars = L"http://+:80/example"; // address given as uri
serviceEndpoint.address.url.length = (ULONG)wcslen(serviceEndpoint.address.url.chars);
serviceEndpoint.channelBinding = WS_HTTP_CHANNEL_BINDING; // channel binding for the endpoint
serviceEndpoint.channelType = WS_CHANNEL_TYPE_REPLY; // the channel type
serviceEndpoint.contract = &calculatorContract; // the contract
serviceEndpoint.properties = serviceEndpointProperties;
serviceEndpoint.propertyCount = WsCountOf(serviceEndpointProperties);
// Create an error object for storing rich error information
hr = WsCreateError(
NULL,
0,
&error);
if (FAILED(hr))
{
goto Exit;
}
// Create Event object for closing the server
closeServer = CreateEvent(
NULL,
TRUE,
FALSE,
NULL);
if (closeServer == NULL)
{
hr = HRESULT_FROM_WIN32(GetLastError());
goto Exit;
}
// Creating a service host
hr = WsCreateServiceHost(
serviceEndpoints,
1,
NULL,
0,
&host,
error);
if (FAILED(hr))
{
goto Exit;
}
// WsOpenServiceHost to start the listeners in the service host
hr = WsOpenServiceHost(
host,
NULL,
error);
if (FAILED(hr))
{
goto Exit;
}
WaitForSingleObject(closeServer, INFINITE);
// Close the service host
hr = WsCloseServiceHost(host, NULL, error);
if (FAILED(hr))
{
goto Exit;
}
Exit:
if (FAILED(hr))
{
// Print out the error
PrintError(hr, error);
}
fflush(
stdout);
if (host != NULL)
{
WsFreeServiceHost(host);
}
if (error != NULL)
{
WsFreeError(error);
}
if (closeServer != NULL)
{
CloseHandle(closeServer);
}
fflush(stdout);
return SUCCEEDED(hr) ? 0 : -1;
}