fortran-nng

A collection of Fortran 2018 ISO C binding interfaces to the lightweight messaging library NNG v1.11.0:

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.

The bindings cover the API of NNG v1 (stable). See branch v2 for bindings to NNG v2. Link your Fortran programs with libfortran-nng.a and libnng.so. If fortran-nng is installed to /opt, run:

$ gfortran -I/opt/include/libfortran-nng -o example example.f90 /opt/lib/libfortran-nng.a -lnng

For Fortran bindings to nanomsg, see nanofort.

Dependencies

On Linux, install NNG with development headers first:

$ sudo apt-get install libnng1 libnng-dev nng-utils

On FreeBSD:

$ doas pkg install net/nng

Alternatively, build NNG simply from source and install it to /opt:

$ git clone --depth 1 --branch v1.11 https://github.com/nanomsg/nng.git
$ mkdir -p nng/build && cd nng/build/
$ cmake -DCMAKE_INSTALL_PREFIX:PATH=/opt ..
$ make
$ make install

Build Instructions

If the NNG library is installed globally, build and install the interfaces library with GNU Fortran by running:

$ make

If you prefer LLVM, run, for example:

$ make CC=clang21 FC=flang21

If the NNG library is installed in /opt, pass the prefix:

$ make PREFIX=/opt

To link against a static libnng.a library instead, run:

$ make LDLIBS="/path/to/libnng.a -lpthread"

Install the fortran-nng library and module files to /opt:

$ make install PREFIX=/opt

Fortran Package Manager

This project supports the Fortran Package Manager (FPM). To build the project with FPM, run:

$ fpm build --profile release

The example programs are available with the fpm run --example command. You can add fortran-nng to your fpm.toml with:

[dependencies]
fortran-nng = { git = "https://github.com/interkosmos/fortran-nng.git" }

Examples

The following programs can be found in directory examples/:

• async implements an asynchronous RPC service.
• bus creates an interconnected mesh network.
• http_client sends an HTTP GET request and outputs the response.
• pair shows one-to-one peer relationship.
• pipeline solves producer/consumer problem with pipeline (one-way pipe).
• pubsub shows pub/sub messaging pattern.
• pubsub_forwarder implements a simple pub/sub forwarder.
• reqrep demonstrates request-response pattern between client and server.
• survey sends a timed survey out.

Build the examples with:

$ make examples

Compatibility

The fortran-nng bindings differ slightly from the C API:

• Derived types do not have to be initialised like in C.
• All strings passed to the NNG interfaces have to be properly null-terminated with constant c_null_char, except for parameter strings already provided by the Fortran modules. You can use function f_c_str() from module nng_util to add the null-termination.
• C string pointers returned by NNG functions are converted to Fortran allocatable character through wrappers. The interfaces are public and end with suffix _.
• The prefix of nng_log_level enumerators has been changed from NNG_LOG_ to NNG_LOG_LEVEL_ due to conflicts with procedures of the same name.
• The prefix of nng_log_facility enumerators has been changed from NNG_LOG_ to NNG_LOG_FACILITY_ due to conflicts with procedures of the same name.
• The interfaces to the NNG log functions expect a single (non-variadic) string argument only.

Source Code Documentation

The source code documentation has to be created with FORD. Install the Python package with:

$ python3 -m pip install -U ford

In the fortran-nng repository, run:

$ make doc

The HTML files will be written to directory doc/. Open index.html in a web browser.

References

• NNG Web Site
• NNG Repository
• NNG Reference Manual
• NNG API Documentation (v1.10.0)
• Getting Started with NNG

Licence

ISC