string - Erlang:将 TCP 发送的字符串转换为正确的形式，例如<<"SomeString">> 到 "SomeString"？

Question

我有一个客户端和一个服务器，我使用客户端发送一个字符串，例如 "Hello"它在服务器端显示为 <<"Hello">> .有没有办法简单地转换 <<"Hello">>返回"Hello" ？我尝试使用，

String = io_lib:format("~p",[StringIn]),
            lists:flatten(String),

但这使得格式为 <<"Hello">>变成[[60,60,"\"Hello\"",62,62]] ...

顺便说下代码:

-module(ss1).
-compile(export_all).
-import(lists, [reverse/1]).

client() ->
    {ok, Socket} =  gen_tcp:connect("localhost", 2345,[binary, {packet, 4}]),
    ok = gen_tcp:send(Socket, "Hello"),
    receive
    {tcp,Socket,String} ->
        io:format("Client received = ~p~n",[String]),       
        io:format("Client result = ~p~n",[String]),
        gen_tcp:close(Socket)
    end.

server() ->
    {ok, Listen} = gen_tcp:listen(2345, [binary, {packet, 4},  {reuseaddr, true}, {active, true}]),
    {ok, Socket} = gen_tcp:accept(Listen),
    gen_tcp:close(Listen),  
    loop(Socket).

loop(Socket) ->
    receive
    {tcp,Socket,String} ->      
        io:format("Server received String = ~p~n",[String]),            
        io:format("Server replying String = ~p~n",[String]),
        gen_tcp:send(Socket, String), 
        loop(Socket);
    {tcp_closed, Socket} ->
        io:format("Server socket closed~n")
    end.

Answer 1

原因是这一行:

{ok, Listen} = gen_tcp:listen(2345, [binary, {packet, 4},  {reuseaddr, true}, {active, true}]),

具体来说，在选项中传递的原子 binary。如果您改为传递 list，您将获得一个常规字符串。查看documentation对于 gen_tcp:listen/2。

以下代码不起作用的原因:

String = io_lib:format("~p",[StringIn]),
lists:flatten(String), ...

是 lists:flatten/1 实际上没有改变 String;它返回一个新列表，该列表是展平其参数的结果。这会奏效:

lists:flatten(io_lib:format("~p", [StringIn])).