Rust FFI bindings to NNG:

NNG, like its predecessors nanomsg (and to some extent ZeroMQ), is a lightweight, broker-less library, offering a simple API to solve common recurring messaging problems, such as publish/subscribe, RPC-style request/reply, or service discovery. The API frees the programmer from worrying about details like connection management, retries, and other common considerations, so that they can focus on the application instead of the plumbing.

Usage

Version of this crate tracks NNG: <NNG_version>-rc.<crate_version> (e.g. 1.1.1-rc.2).

To use the latest crate for the most recent stable version of NNG (1.4.x), in Cargo.toml:

[dependencies]
nng-sys = "1.4.0-rc"

Requirements:

• cmake v3.13 or newer in PATH
  • On Linux/macOS: default generator is "Unix Makefiles"
  • On Windows: default generator is generally latest version of Visual Studio installed
• Optional libclang needed if using build-bindgen feature to run bindgen

Features

• build-nng: use cmake to build NNG from source (enabled by default)
• build-bindgen: run bindgen to re-generate Rust FFI bindings to C
• cmake-unix: use cmake generator "Unix Makefiles" (default on Linux/macOS)
• cmake-ninja: use cmake generator "Ninja"
• cmake-vs2017: use cmake generator "Visual Studio 15 2017"
• cmake-vs2019: use cmake generator "Visual Studio 16 2019"
• nng-stats: enable NNG stats NNG_ENABLE_STATS (enabled by default)
• nng-tls: enable TLS NNG_ENABLE_TLS (requires mbedTLS)
• nng-supplemental: generate bindings to NNG's supplemental functions
• nng-compat: generate bindings to NNG's nanomsg compatible functions

Example) Re-generate FFI bindings with bindgen:

[dependencies]
nng-sys = { version = "1.4.0-rc", features = ["build-bindgen"] }

Example) Disable stats and use Ninja cmake generator:

[dependencies.nng-sys]
version = "1.4.0-rc"
default-features = false
features = ["cmake-ninja"]

Examples

use nng_sys::*;
use std::{ffi::CString, os::raw::c_char, ptr::null_mut};

fn example() {
    unsafe {
        let url = CString::new("inproc://nng_sys/tests/example").unwrap();
        let url = url.as_bytes_with_nul().as_ptr() as *const c_char;

        // Reply socket
        let mut rep_socket = nng_socket::default();
        nng_rep0_open(&mut rep_socket);
        nng_listen(rep_socket, url, null_mut(), 0);

        // Request socket
        let mut req_socket = nng_socket::default();
        nng_req0_open(&mut req_socket);
        nng_dial(req_socket, url, null_mut(), 0);

        // Send message
        let mut req_msg: *mut nng_msg = null_mut();
        nng_msg_alloc(&mut req_msg, 0);
        // Add a value to the body of the message
        let val = 0x12345678;
        nng_msg_append_u32(req_msg, val);
        nng_sendmsg(req_socket, req_msg, 0);

        // Receive it
        let mut recv_msg: *mut nng_msg = null_mut();
        nng_recvmsg(rep_socket, &mut recv_msg, 0);
        // Remove our value from the body of the received message
        let mut recv_val: u32 = 0;
        nng_msg_trim_u32(recv_msg, &mut recv_val);
        assert_eq!(val, recv_val);
        // Can't do this because nng uses network order (big-endian)
        //assert_eq!(val, *(nng_msg_body(recv_msg) as *const u32));

        nng_close(req_socket);
        nng_close(rep_socket);
    }
}