平时做技术实践时，很多问题不是概念不会，而是细节没串起来。拿“Erlang实现方法的一个Web服务器代码实例”来说，它看着像小点，放到项目里常会牵出环境、配置、兼容性和维护成本。下面按实际采用顺序，把思路、关键写法和容易踩坑的地方讲清楚，便于大家直接对照操作。
转贴一个轻松的Web服务器：
httpd.erl
%% httpd.erl - MicroHttpd
-module(httpd).
-author("[email protected]").
-export([start/0,start/1,start/2,process/2]).
-import(regexp,[split/2]).
-define(defPort,8888).
-define(docRoot,"public").
start() -> start(?defPort,?docRoot).
start(Port) -> start(Port,?docRoot).
start(Port,DocRoot) ->
case gen_tcp:listen(Port, [binary,{packet, 0},{active, false}]) of
{ok, LSock} -> server_loop(LSock,DocRoot);
{error, Reason} -> exit({Port,Reason})
end.
%% main server loop - wait for next connection, spawn child to process it
server_loop(LSock,DocRoot) ->
case gen_tcp:accept(LSock) of
{ok, Sock} ->
spawn(?MODULE,process,[Sock,DocRoot]),
server_loop(LSock,DocRoot);
{error, Reason} ->
exit({accept,Reason})
end.
%% process current connection
process(Sock,DocRoot) ->
Req = do_recv(Sock),
{ok,[Cmd|[Name|[Vers|_]]]} = split(Req,"[ rn]"),
FileName = DocRoot ++ Name,
LogReq = Cmd ++ " " ++ Name ++ " " ++ Vers,
Resp = case file:read_file(FileName) of
{ok, Data} ->
io:format("~p ~p ok~n",[LogReq,FileName]),
Data;
{error, Reason} ->
io:format("~p ~p failed ~p~n",[LogReq,FileName,Reason]),
error_response(LogReq,file:format_error(Reason))
end,
do_send(Sock,Resp),
gen_tcp:close(Sock).
%% construct HTML for failure message
error_response(LogReq,Reason) ->
"<html><head><title>Request Failed</title></head><body>n" ++
"<h1>Request Failed</h1>n" ++ "Your request to " ++ LogReq ++
" failed due to: " ++ Reason ++ "n</body></html>n".
%% send a line of text to the socket
do_send(Sock,Msg) ->
case gen_tcp:send(Sock, Msg) of
ok -> ok;
{error, Reason} -> exit(Reason)
end.
%% receive data from the socket
do_recv(Sock) ->
case gen_tcp:recv(Sock, 0) of
{ok, Bin} -> binary_to_list(Bin);
{error, closed} -> exit(closed);
{error, Reason} -> exit(Reason)
end
从实现思路看，运行时在httpd.erl本地建一个public目录，public目录里放一个index.html文件
随后httpd:start()启动服务器，就能够访问（链接已移除）
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