The SMC-R protocol is transparent to and fully compatible with TCP socket applications. A wide range of functions are available through the API interfaces that z/OS® Communications Server provides. The use of SMC-R protocols for exchanging application socket data is not apparent to the applications. Thus, socket API functions such as MSGWAITALL, MSG_PEEK, Accept and Receive (ANR), and Urgent Data can still be used by the applications, even when SMC-R communications are used.