如何使用ListenSocket的PORT的环境变量启动iex

Question

我已经为我的应用程序创建了一个服务器和一个客户端部分，我想用不同的端口启动每个节点，我想使用环境变量来实现这一点，这怎么可能？这是服务器代码：

defmodule Multichat.Server do
require Logger

def accept(port) do
{:ok, socket} = :gen_tcp.listen(port, [:binary, packet: :line, active: true, reuseaddr: true])
Logger.info "Accepting connections on port #{port}"
loop_acceptor(socket)
end
defp loop_acceptor(socket) do
{:ok, client} = :gen_tcp.accept(socket)
{:ok, pid} = DynamicSupervisor.start_child(Multichat.Server.ConnectionSupervisor, {Multichat.ClientConnection, client})
:ok = :gen_tcp.controlling_process(client, pid)
loop_acceptor(socket)
end
end

客户端连接代码：

defmodule Multichat.ClientConnection do
use GenServer
def start_link(socket), do: GenServer.start_link(__MODULE__, socket)
def init(init_arg) do
{:ok, init_arg}
end
def handle_call({:send, message}, _from, socket) do
:gen_tcp.send(socket, message)
{:reply, :ok, socket}
end
def handle_info({:tcp, _socket, message}, socket) do
for {_, pid, _, _} <- DynamicSupervisor.which_children(Multichat.Server.ConnectionSupervisor) do
if pid != self() do
GenServer.call(pid, {:send, message})
end
end
{:noreply, socket}
end
end

完整的代码在这里

Answer 1

您正在查找System.get_env/2。

例如，您可以将Multichat.Server.accept/1函数修改为类似于：

def accept(port \ nil)
def accept(nil) do
"MY_PORT"
|> System.get_env("6789")
|> String.to_integer()
|> accept()
end
def accept(port) do
{:ok, socket} = :gen_tcp.listen(port, [:binary, packet: :line, active: true, reuseaddr: true])
Logger.info "Accepting connections on port #{port}"
loop_acceptor(socket)
end