greeting_app — Canopy TCP example

A minimal two-process example using the Canopy RPC library. A server exposes a i_greeter interface over TCP; a client connects, calls three methods, and exits.

Prerequisites

• Canopy checked out at ../Canopy (adjacent to this directory)
• clang / clang++ (default; see CMakePresets.json to override)
• Ninja
• OpenSSL, liburing (same requirements as Canopy coroutine builds)

Build

cmake --preset Coroutine
cmake --build build_coroutine --target server client

Binaries land in build_coroutine/output/.

Running

Start the server in one terminal, then run the client in another.

Server

./build_coroutine/output/server [options]

Press Ctrl+C to shut down.

Client

./build_coroutine/output/client [options]

The client connects, calls greet, add, and get_server_info, prints the results, then exits cleanly.

Command-line options

Both server and client register Canopy network arguments via canopy::network_config::add_network_args(parser).

Virtual-address options

These options define the Canopy zone address allocated for the local process:

Option	Meaning
--va-name <identifier>	Virtual address name.
`--va-type <local	ipv4
--va-prefix <prefix>	Routing prefix. If omitted, Canopy auto-detects it.
--va-subnet-bits <n>	Subnet field width. Default in Canopy is 64.
--va-subnet <value>	Initial subnet value. Default in Canopy is 0.
--va-object-id-bits <n>	Object-id field width. Default in Canopy is 64.
--va-object-id <value>	Initial object-id value. Default in Canopy is 0.

Physical endpoint options

These options define the TCP addresses used for listening and connecting:

Option	Meaning
--listen [va-name:]addr:port	Server bind/listen endpoint.
--connect [va-name:]addr:port	Client connect endpoint.
-h, --help	Print usage and exit.

Address family is inferred from the endpoint format:

• IPv4: 127.0.0.1:8080
• IPv6: [::1]:8080
• Port-only listen form: 9090

Defaults in This Example

This repo adds defaults before parsing CLI arguments, so the programs run without manually specifying Canopy network flags.

Server defaults

If you do not pass any --va-* options, server injects:

--va-name=server
--va-type=ipv4
--va-prefix=127.0.0.1
--va-subnet-bits=32
--va-object-id-bits=32
--va-subnet=1

If you do not pass --listen, server injects:

--listen=server:127.0.0.1:8080

Client defaults

If you do not pass any --va-* options, client injects:

--va-name=client
--va-type=ipv4
--va-prefix=127.0.0.1
--va-subnet-bits=32
--va-object-id-bits=32
--va-subnet=100

If you do not pass --connect, client injects:

--connect=client:127.0.0.1:8080

Examples

Default (loopback, port 8080):

# terminal 1
./build_coroutine/output/server

# terminal 2
./build_coroutine/output/client

Custom port:

./build_coroutine/output/server --listen=server:127.0.0.1:9000
./build_coroutine/output/client --connect=client:127.0.0.1:9000

Custom virtual-address prefixes and endpoint port:

./build_coroutine/output/server \
  --va-name=server --va-type=ipv4 --va-prefix=192.168.1.0 \
  --va-subnet-bits=32 --va-object-id-bits=32 --va-subnet=1 \
  --listen=server:192.168.1.10:9000

./build_coroutine/output/client \
  --va-name=client --va-type=ipv4 --va-prefix=192.168.1.0 \
  --va-subnet-bits=32 --va-object-id-bits=32 --va-subnet=100 \
  --connect=client:192.168.1.10:9000

IPv6:

./build_coroutine/output/server \
  --va-name=server --va-type=ipv6 --va-prefix=2001:db8:: \
  --listen=server:[::1]:8080

./build_coroutine/output/client \
  --va-name=client --va-type=ipv6 --va-prefix=2001:db8:: \
  --connect=client:[::1]:8080

IDL interface

Defined in idl/greeting/greeting.idl:

namespace greeting_app
{
    interface i_greeter
    {
        int greet([in] const std::string& name, [out] std::string& response);
        int add(int a, int b, [out] int& result);
        int get_server_info([out] std::string& info);
    };
}

Generated code appears in build_coroutine/generated/ and is never written back into the source tree.

Project layout

test_app/
├── CMakeLists.txt              root build file; pulls in Canopy via add_subdirectory
├── CMakePresets.json           Coroutine (Debug) and Release_Coroutine presets
├── idl/
│   ├── CMakeLists.txt          CanopyGenerate() call
│   └── greeting/
│       └── greeting.idl        i_greeter interface definition
└── src/
    ├── server.cpp              greeter_impl + TCP listener; runs until Ctrl+C
    └── client.cpp              connects, calls all three methods, exits