Erlang:将TCP发送的字符串转换为正确的形式,例如<<"SomeString">>转换为"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"Hello",它在服务器端显示为<<"Hello">>.有没有办法简单地转换<<"Hello">>回来"Hello"？我试过用,

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

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

顺便提一下代码:

-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,原子binary在选项中传递.如果你通过list,你会得到一个常规的字符串.查看文档的gen_tcp:listen/2.

以下代码不起作用的原因:

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

这lists:flatten/1实际上并没有改变 String ; 它返回一个新列表,它是展平其参数的结果.这会有效:

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