网络授时服务是一些网络上的时间服务器提供的时间，一般用于本地时钟同步。 授时服务有很多种，一般我们选择RFC-868。这个协议的工作流程是：（S代表Server，C代表Client）
S: 检测端口37
U: 连接到端口37
S: 以32位二进制数发送时间
U: 接收时间
U: 关闭连接
S: 关闭连接
协议非常简单，用TCP连接上后，服务器直接把时间发送回来。发送的是从1900年1月1日午夜到现在的秒数。
使用luasocket
实现的方案有很多种，Lua不一定是最简单的，选择只是出于个人兴趣。直接上代码吧
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------------------------------------------------------------------------------- Network Time Protocal-- Author: ani_di-----------------------------------------------------------------------------package.cpath = package.cpath .. ';D:\\tools\\Lua\\5.1\\clibs\\?.dll;?.dll'local socket = require "socket.core"server_ip = { -- "129.6.15.29", "132.163.4.101", "132.163.4.102", "132.163.4.103", "128.138.140.44", "192.43.244.18", "131.107.1.10", "66.243.43.21", "216.200.93.8", "208.184.49.9", "207.126.98.204", "207.200.81.113", "205.188.185.33"}function nstol(str) assert(str and #str == 4) local t = {str:byte(1,-1)} local n = 0 for k = 1, #t do n= n*256 + t[k] end return nend-- get time from a ip address, use tcp protoclfunction gettime(ip) print('connect ', ip) local tcp = socket.tcp() tcp:settimeout(10) tcp:connect(ip, 37) success, time = pcall(nstol, tcp:receive(4)) tcp:close() return success and time or nilendfunction nettime() for _, ip in pairs(server_ip) do time = gettime(ip) if time then return time end endend |
代码原理不细说，非常简单。唯一值得一提的是socket库包含。最开始用的这句 require "socket"
在解释器中表现很好，但在用C中调用会找不到相应的module。错误提示
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no field package.preload['socket']no file '.\socket.lua'no file 'F:\Projects\Lua\nettime\lua\socket.lua'no file 'F:\Projects\Lua\nettime\lua\socket\init.lua'no file 'F:\Projects\Lua\nettime\socket.lua'no file 'F:\Projects\Lua\nettime\socket\init.lua'no file 'D:\tools\Lua\5.1\lua\socket.luac'no file '.\socket.dll'no file '.\socket51.dll'no file 'F:\Projects\Lua\nettime\socket.dll'no file 'F:\Projects\Lua\nettime\socket51.dll'no file 'F:\Projects\Lua\nettime\clibs\socket.dll'no file 'F:\Projects\Lua\nettime\clibs\socket51.dll'no file 'F:\Projects\Lua\nettime\loadall.dll'no file 'F:\Projects\Lua\nettime\clibs\loadall.dll'. |
网上也有好多类似的提问，大抵是没仔细看作者的Guide。显著的有这么一句
The other two environment variables instruct the compatibility module to look for dynamic libraries and extension modules in the appropriate directories and with the appropriate filename extensions.>
LUAPATH=/?.lua;?.lua LUACPATH=/?.dll;?.dll
至于"socket.core"，windows默认安装位于“\socket\core.dll”。
C宿主调用
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#include <stdio.h>#include <string.h>#include <lua.h>#include <lauxlib.h>#include <lualib.h>#include <time.h>#include <Windows.h>int load(lua_State* L, const char* func, unsigned int* utc) { lua_getglobal(L, func); if (lua_pcall(L, 0, 1, 0)) { printf("Error Msg pcall %s.\n", lua_tostring(L, -1)); return -1; } if (!lua_isnumber(L,-1)) { printf("time should be a number\n" ); return -2; } *utc = lua_tonumber(L,-1); lua_pop(L, -1); return 0;}void TimetToFileTime( time_t t, LPFILETIME pft ){ LONGLONG ll = Int32x32To64(t, 10000000) + 116444736000000000; pft->dwLowDateTime = (DWORD) ll; pft->dwHighDateTime = ll >>32;}int main(){ lua_State* L = luaL_newstate(); unsigned int utc = 0; luaL_openlibs(L); if (luaL_loadfile(L, "nettime.lua") || lua_pcall(L, 0, 0, 0)) { printf("Error Msg load %s.\n", lua_tostring(L, -1)); return -1; } do { if(load(L,"nettime", &utc) == 0) { time_t tt = utc - 2208988800L; SYSTEMTIME st; FILETIME ft; TimetToFileTime(tt, &ft); if (FileTimeToSystemTime(&ft, &st)) { printf("Today is: %d-%d-%d\n", st.wYear, st.wMonth, st.wDay); SetSystemTime(&st); } break; } else { puts("No network!"); Sleep(10000); } } while (1); lua_close(L); return 0;} |
