Lua Socket

LuaSockets allow a widget to use tcp/udp sockets. With luasockets you can create a client or a server connecting to a server and transfering some data.

There are many possibilties what could be done with luasockets in spring, some ideas:

• webserver that shows all files in VFS
• telnet console, that allows control of spring
• statistics webpage
• ingame widget updater
• ingame news pages
• ...

config

All LuaSocket related config is readonly for LuaWidgets. They can be only changed through unitsync.

As default, socket access is restricted, as default no connections are allowed. To allow a connection / sending a packet, the destination has to the corresponding allow rule. For example, if a lua widget wants to connect to springrts.com at port 80,

TCPAllowConnect springrts.com:80

has to be set.

Since spring 97.0 lobby.springrts.com:8200 is allowed as default.

Since Spring 98.0 all tcp connections are allowed by default (udp is still restricted).

Creating a server socket needs no config value to be set.

possible config values

LuaSocketEnabled = 1	Default is 1 means, all Socket functions are enabled, 0 disables access to sockets.
TCPAllowConnect	allow TCP-connections to the listed hosts, for example: "springrts.com:80 springfiles.com:80" which allows luasockets to connect to springrts.com at port 80 and springfiles.com at port 80.
UDPAllowConnect	see TCPAllowConnect

example code

• luasocket.lua
• luasocket_console.lua

Notes / known issues / TODO

• only ipv4 is supported (could be solved by using unstable luasocket2: http://code.matthewwild.co.uk/luasocket2-hg/) or https://github.com/diegonehab/luasocket (seems to be the more official)
• dns resolving is blocking, solutions: worker thread or some lib:
  • adns http://www.chiark.greenend.org.uk/~ian/adns/
  • dns.c http://25thandclement.com/~william/projects/dns.c.html
  • tadns http://adns.sourceforge.net/
  • or a lua implementation? biggest problem would be to find the local dns-server
• most lua scripts from luasocket won't work as they are blocking! rewriting them non-blocking is required! (should be in most cases few work, as parsing stuff can be reused)
• config file should be better protected, see https://github.com/spring/spring/blob/develop/rts/System/Config/ConfigHandler.cpp#L289 + https://github.com/spring/spring/commit/948d6fb9d1c95b99b5cc7929cf3e0de0f9d6d93e maybe just locking the file is best?! see also http://springrts.com/mantis/view.php?id=2891 (private report)
• access to autohost interface / game host is denied
• If you get this error:

Error in Initialize(): [string "LuaUI/Widgets/luasocket.lua"]:65:
attempt to index upvalue 'socket' (a nil value)

you maybe need to add to system.lua: socket = socket,

documentation

• http://w3.impa.br/~diego/software/luasocket/socket.html
• http://w3.impa.br/~diego/software/luasocket/tcp.html
• http://w3.impa.br/~diego/software/luasocket/udp.html

links

lua sockets in spring - original thread Lua Lobby / Socket - some code pieces for connecting to spring lobby server & protocol