Protocols

libevpl has built-in support for multiple network protocols. Each protocol has a unique identifier used when creating connections or listeners.

Protocol Types

Stream Protocols

Stream protocols provide reliable, ordered byte streams:

Protocol ID	Description
`EVPL_STREAM_SOCKET_TCP`	Standard TCP sockets via the kernel
`EVPL_STREAM_SOCKET_TLS`	TLS-encrypted TCP connections
`EVPL_STREAM_IO_URING_TCP`	TCP using io_uring for improved performance
`EVPL_STREAM_RDMACM_RC`	RDMA Reliable Connection (RC) via RDMACM

Datagram Protocols

Datagram protocols provide message-oriented communication:

Protocol ID	Description
`EVPL_DATAGRAM_SOCKET_UDP`	Standard UDP datagrams
`EVPL_DATAGRAM_RDMACM_UD`	RDMA Unreliable Datagram (UD)
`EVPL_DATAGRAM_TCP_RDMA`	RDMA emulation over TCP (see below)

TCP-RDMA Protocol

The EVPL_DATAGRAM_TCP_RDMA protocol provides RDMA semantics over standard TCP sockets. This enables development and testing of RDMA-based applications without requiring RDMA hardware.

Despite being implemented over TCP (a stream protocol), TCP-RDMA presents a datagram-style message interface because it emulates RDMA operations which are inherently message-based.

Use cases:

Development without RDMA hardware
CI/CD testing in virtualized environments
Debugging RDMA protocols with standard network tools
Cross-platform RDMA application support

See the RDMA API documentation for details on using TCP-RDMA.

Frameworks

Frameworks are the underlying I/O implementations that protocols use:

Framework ID	Description
`EVPL_FRAMEWORK_SOCKET`	Standard kernel sockets (epoll/kqueue)
`EVPL_FRAMEWORK_RDMACM`	RDMA Connection Manager
`EVPL_FRAMEWORK_IO_URING`	Linux io_uring
`EVPL_FRAMEWORK_VFIO`	VFIO for userspace device access
`EVPL_FRAMEWORK_TLS`	TLS/SSL via OpenSSL
`EVPL_FRAMEWORK_TCP_RDMA`	TCP-based RDMA emulation

Protocol Selection

Use evpl_protocol_lookup to convert a protocol name string to its ID:

enum evpl_protocol_id proto;
int rc = evpl_protocol_lookup(&proto, "STREAM_SOCKET_TCP");
if (rc == 0) {
    /* proto now contains EVPL_STREAM_SOCKET_TCP */
}

Common protocol name strings:

"STREAM_SOCKET_TCP" - TCP
"STREAM_SOCKET_TLS" - TLS over TCP
"DATAGRAM_SOCKET_UDP" - UDP
"STREAM_RDMACM_RC" - RDMA RC
"DATAGRAM_TCP_RDMA" - TCP-RDMA emulation