I have a program with three WCF services and when I run them locally (i.e: Server and Clients are all on localhost) everything works. However when I test them across a network I get a TimoutException on two services but not the other. I've disabled the firewalls on all the machines involved in the test. I can both ping the server and access the wsdl "You have created a service" webpage from the client The service that works uses a BasicHttpBinding with streaming and the two which don't work use WSDualHttpBinding. The Services that use WSDualHttpBinding both have CallbackContracts. I apologise for the vagueness of this question but I'm not really sure what code to include or where to even start looking for the solution to this. Non-working bindings: public static Binding CreateHTTPBinding() { var binding = new WSDualHttpBinding(); binding.MessageEncoding = WSMessageEncoding.Mtom; binding.MaxBufferPoolSize = 2147483647; binding.MaxReceivedMessageSize = 2147483647; binding.Security.Mode = WSDualHttpSecurityMode.None; return binding; } Exception Stack Trace: Unhandled Exception: System.TimeoutException: The open operation did not complete within the allotted timeout of 00:01:00. The time allotted to this operation may have been a portion of a longer timeout. Server stack trace: at System.ServiceModel.Channels.ReliableRequestor.ThrowTimeoutException() at System.ServiceModel.Channels.ReliableRequestor.Request(TimeSpan timeout) at System.ServiceModel.Channels.ClientReliableSession.Open(TimeSpan timeout) at System.ServiceModel.Channels.ClientReliableDuplexSessionChannel.OnOpen(TimeSpan timeout) at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannel.OnOpen(TimeSpan timeout) at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannel.CallOpenOnce.System.ServiceModel.Channels.ServiceChannel.ICallOnce.Call(ServiceChannel channel, TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannel.CallOnceManager.CallOnce(TimeSpan timeout, CallOnceManager cascade) at System.ServiceModel.Channels.ServiceChannel.EnsureOpened(TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs) at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation) at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message) Exception rethrown at [0]: at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg) at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type) at IDemeService.Register() at DemeServiceClient.Register() at DemeClient.Client.Start() at DemeClient.Program.Main(String[] args)