[英]TCP Listener on Elixir using Erlang's gen_tcp module
I am using the following code to create a TCP listener on elixir : 我使用以下代码在elixir上创建TCP侦听器:
defmodule KVServer do
use Application
@doc false
def start(_type, _args) do
import Supervisor.Spec
children = [
supervisor(Task.Supervisor, [[name: KVServer.TaskSupervisor]]),
worker(Task, [KVServer, :accept, [4040]])
]
opts = [strategy: :one_for_one, name: KVServer.Supervisor]
Supervisor.start_link(children, opts)
end
@doc """
Starts accepting connections on the given `port`.
"""
def accept(port) do
{:ok, socket} = :gen_tcp.listen(port,
[:binary, packet: :line, active: false, reuseaddr: true])
IO.puts "Accepting connections on port #{port}"
loop_acceptor(socket)
end
defp loop_acceptor(socket) do
{:ok, client} = :gen_tcp.accept(socket)
{:ok, pid} = Task.Supervisor.start_child(KVServer.TaskSupervisor, fn -> serve(client) end)
:ok = :gen_tcp.controlling_process(client, pid)
loop_acceptor(socket)
end
defp serve(socket) do
socket
|> read_line()
|> write_line(socket)
serve(socket)
end
defp read_line(socket) do
{:ok, data} = :gen_tcp.recv(socket, 0)
data
end
defp write_line(line, socket) do
:gen_tcp.send(socket, line)
end
end
It is taken from the following link: http://elixir-lang.org/getting-started/mix-otp/task-and-gen-tcp.html 它取自以下链接: http : //elixir-lang.org/getting-started/mix-otp/task-and-gen-tcp.html
When I try to get data from my gps deveice (for which I am writing this piece of code) using :gen_tcp.recv(socket,0), I get an error: {:error, reason} = :gen_tcp.recv(socket, 0)
and the reason it showed is just "closed". 当我尝试使用:gen_tcp.recv(socket,0)从我的gps deveice(我正在编写这段代码)中获取数据时,我收到一个错误: {:error, reason} = :gen_tcp.recv(socket, 0)
它显示的原因只是“关闭”。
However, the device is sending data, which I confirmed using a tcp packet sniffer (tcpflow). 但是,设备正在发送数据,我使用tcp数据包嗅探器(tcpflow)确认了该数据。
Also, when I try to send data using telnet as described in the tutorial above, it works fine. 此外,当我尝试使用上面的教程中描述的telnet发送数据时,它工作正常。
Any help would be highly appreciated. 任何帮助将受到高度赞赏。
I was finally able to figure it out. 我终于弄清楚了。 Actually the device was sending raw stream of data not lines of data. 实际上,该设备正在发送原始数据流而不是数据行。 So I had to change "packet: :line" parameter in :gen_tcp.listen function to "packet: :raw". 所以我不得不将gen_tcp.listen函数中的“packet :: line”参数改为“packet :: raw”。
It was working on telnet because telnet sends lines of data (with line breaks). 它正在telnet上工作,因为telnet发送数据行(带换行符)。
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