Leave endpoint hostname empty if it does not resolve

If the hostname does not resolve to a valid IP address the
function from the system package reports "0.0.0.0". In this
case we leave endpoint host/ip part empty to fall back to
the default behaviour.

src/daemon/pmgserver.cxx

@@ -62,14 +62,25 @@ int main(int argc, char** argv) {
 		try {
 			// Get the port number to use in CORBA communications, maybe 0
 			portNumber = daq::pmg::utils::serverPort();
-            std::ostringstream portNumber_str;
+
+            // Get numerical host IP - this may fail if the gethostname() does not
+            // resolve to one of the network interfaces. In this case leave the
+            // hostname port of the endpoint empty.
+            std::string ip = System::LocalHost::instance()->ip_string();
+            if(ip == "0.0.0.0") {
+                ip = "";
+            }
 
             // Note: always use TLS
-            portNumber_str << "giop:ssl:" << System::LocalHost::instance()->ip_string() << ":" << portNumber;
-            std::pair<std::string, std::string> addedOpt = std::make_pair("endPoint", portNumber_str.str());
+            std::ostringstream endpoint_str;
+            endpoint_str << "giop:ssl:" << ip << ":";
+            if(portNumber != 0) {
+                endpoint_str << portNumber;
+            }
+            std::pair<std::string, std::string> addedOpt = std::make_pair("endPoint", endpoint_str.str());
             optList.push_back(addedOpt);
             // Only publish the TLS endpoint, and only on the 'control' interface, i.e. the one that reverse resolves to the hostname
-            optList.push_back(std::pair("endPointPublish", "giop:ssl:" + System::LocalHost::instance()->ip_string() + ":"));
+            optList.push_back(std::pair("endPointPublish", "giop:ssl:" + ip + ":"));
 		}
 		catch(daq::pmg::IPC_Port_Error &ex) {
 			ers::fatal(ex);