The purpose of Windows Workflow Foundation is that provides a programming model, in-process workflow engine and rehostable designer to implement long-running processes as workflows within .NET applications. You may implement your network protocol and use
it in a custom activity, however this is out of Workflow Foundation scope, you may get better support at
NET Framework Networking and Communication
In addition, if you want to communicate across the web and the enterprise, Windows Communication Foundation(WCF) is recommended. "By the time we’re done, you’ll see that WCF 4 becomes easier to use and provides more built-in support for some of today’s most
common scenarios and development styles." Also, WCF providers rich integration with Windows Workflow Foundation.