packer-cn/packer/plugin/plugin.go

// The packer/plugin package provides the functionality required for writing
// Packer plugins in the form of static binaries that are then executed and
// run. It also contains the functions necessary to run these external plugins.
package plugin

import (
	"fmt"
	"github.com/mitchellh/packer/packer"
	"net"
	"net/rpc"
	"os"
	packrpc "github.com/mitchellh/packer/packer/rpc"
)

// This serves a single RPC connection on the given RPC server on
// a random port.
func serve(server *rpc.Server) (err error) {
	listener, err := net.Listen("tcp", ":2345")
	if err != nil {
		return
	}
	defer listener.Close()

	// Output the address to stdout
	fmt.Println(":2345")
	os.Stdout.Sync()

	// Accept a connection
	conn, err := listener.Accept()
	if err != nil {
		return
	}

	// Serve a single connection
	server.ServeConn(conn)
	return
}

// Serves a command from a plugin.
func ServeCommand(command packer.Command) {
	server := rpc.NewServer()
	packrpc.RegisterCommand(server, command)

	if err := serve(server); err != nil {
		panic(err)
	}
}