tls_read and tls_write Using similar semantics makes it easy to convert an existing program to use TLS. But we can't quite use the same semantics. These are not single system calls. Our goal is to make tls_read and tls_write similar enough that someone used to read() and write() can use it with a minimum of fuss. We want to make it easy to add TLS to existing code that uses read() and write();