Erlang简易文件服务器和客户端

来自《Erlang程序设计》，该程序包含了Erlang中最基本的消息传递，模式匹配等要素。

Server端

-module(afile_server).
-export([start/1, loop/1]).

start(Dir) -> spawn(afile_server, loop, [Dir]).

loop(Dir) ->
    receive
        {Client, list_dir} ->
            Client ! {self(), file:list_dir(Dir)};
        {Client, {get_file, File}} ->
            Full = filename:join(Dir, File),
            Client ! {self(), file:read_file(Full)}
        end,
        loop(Dir).

首先调用afile_server:start()运行Server进程，并保存其返回的Pid供客户端使用。Server中只匹配list_dir和get_file两种消息，分别返回指定目录下的文件和文件内容。

Client端

-module(afile_client).
-export([ls/1, get_file/2]).

ls(Server) ->
    Server ! {self(), list_dir},
    receive
        {Server, List} ->
            List
    end.
    
get_file(Server, File) ->
    Server ! {self(), {get_file, File}},
    receive
        {Server, Content} ->
            Content
    end.

Client端以Server端Pid为参数，ls()函数会发送list_dir原子给服务器，等待返回的消息。

get_file()函数以Server端Pid和文件名为消息，等待返回的文件内容。

 

首先编译

Erlang/OTP 17 [erts-6.0] [64-bit] [smp:4:4] [async-threads:10]

Eshell V6.0  (abort with ^G)
1> c(afile_server).
{ok,afile_server}
2> c(afile_client).
{ok,afile_client}

开启Server

3> Server = afile_server:start(".").
<0.44.0>

Client

4> afile_client:ls(Server).                 
{ok,["afile_client.beam","afile_client.erl",
     "afile_server.beam","afile_server.erl","Hello.txt",
     "include","lib","min.beam","min.erl","reverse.beam",
     "reverse.erl"]}
5> afile_client:get_file(Server, "Hello.txt").
{ok,<<"Hello,Erlang.">>}