Techniques are described for managing communications with applications executing in a distributed computing environment, through use of a tunneling protocol that is employed by a client-side gateway and a server-side application router to enable client-server communications that would not otherwise be supported within the distributed computing environment. A cloud computing service may enforce network security policies, such as restricting network traffic to and from its hosted applications to use an application layer protocol such as a version of Hypertext Transfer Protocol (HTTP), which may not be feasible for legacy applications and/or applications of a particular type or domain. The implementations described herein provide a mechanism that supports the deployment and operation of an application in a cloud computing environment, where such an application may employ any suitable communication protocol that may not be supported by the environment.