基于TCP的RPC服务

TCP服务器上的RPC，通过创建一个服务器进程监听传入的tcp连接，并允许用户通过此TCP流执行RPC命令

-module(tr_server).
-author("chen").
-behaviour(gen_server).%% API
-export([start_link/1,start_link/0,get_count/0,stop/0
]).-export([init/1, handle_call/3, handle_cast/2, handle_info/2,terminate/2, code_change/3]).-define(SERVER, ?MODULE).
-define(DEFAULT_PORT, 8000).-record(state, {port, lsock, request_count = 0}).start_link(Port) ->gen_server:start_link({local, ?SERVER}, ?MODULE, [Port], []).start_link() ->start_link(?DEFAULT_PORT).
get_count() ->gen_server:call(?SERVER, get_count).
stop() ->gen_server:cast(?SERVER, stop).init([Port]) ->{ok, LSock} = gen_tcp:listen(Port, [{active, true}]),{ok, #state{port = Port, lsock = LSock}, 0}.handle_call(get_count, _From, State) ->{reply, {ok, State#state.request_count}, State}.handle_cast(stop, State) ->{stop, normal, State}.handle_info({tcp, Socket, RawData}, State) ->do_rpc(Socket, RawData),RequestCount = State#state.request_count,{noreply, State#state{request_count = RequestCount + 1}};
handle_info(timeout, #state{lsock = LSock} = State) ->{ok, _Sock} = gen_tcp:accept(LSock),{noreply, State}.terminate(_Reason, _State) ->ok.code_change(_OldVsn, State, _Extra) ->{ok, State}.do_rpc(Socket, RawData) ->try{M, F, A} = split_out_mfa(RawData),Result = apply(M, F, A),gen_tcp:send(Socket, io_lib:fwrite("~p~n", [Result]))catch_Class:Err ->gen_tcp:send(Socket, io_lib:fwrite("~p~n", [Err]))end.split_out_mfa(RawData) ->MFA = re:replace(RawData, "\r\n$", "", [{return, list}]),{match, [M, F, A]} =re:run(MFA,"(.*):(.*)\s*\\((.*)\s*\\)\s*.\s*$",[{capture, [1,2,3], list}, ungreedy]),{list_to_atom(M), list_to_atom(F), args_to_terms(A)}.args_to_terms(RawArgs) ->{ok, Toks, _Line} = erl_scan:string("[" ++ RawArgs ++ "]. ", 1),{ok, Args} = erl_parse:parse_term(Toks),Args.

处理TCP上的RPC请求

do_rpc(Socket, RawData) ->
try
{M, F, A} = split_out_mfa(RawData),
Result = apply(M, F, A),
gen_tcp:send(Socket, io_lib:fwrite("~p~n", [Result]))
catch
_Class:Err ->
gen_tcp:send(Socket, io_lib:fwrite("~p~n", [Err]))
end.

在 split_out_mfa(RawData)中，解析请求数据，随后，将模块名、函数名、参数项式列表传给内置函数apply/，执行请求中的调用。最后，该函数的返回值由io_lib:fwrite/2转换为格式化文本，用作回传给用户的响应，通过套接字发送回去。

split_out_mfa(RawData) ->
MFA = re:replace(RawData, "\r\n$", "", [{return, list}]),
{match, [M, F, A]} =
re:run(MFA,
"(.*):(.*)\s*\$(.*)\s*\$\s*.\s*$",
[{capture, [1,2,3], list}, ungreedy]),
{list_to_atom(M), list_to_atom(F), args_to_terms(A)}.

在 split_out_mfa(RawData)中，解析请求中的字符串。

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