NodeMCU wifi disconnected after several hours

Question

I just started using NodeMCU with Lua. For a start, I am trying to make a simple wifi controlled relay with NodeMCU as a UDP server. The problem is, after running for several hours, I can't make a connection to the board. I tried pinging the board using the ping command, but got no response. If I restart the board, it works again. Any ideas why? Thanks.

Here is my Lua script:

pin_relay = 1
port = 1310
state = 0
gpio.mode(pin_relay, gpio.OUTPUT)
gpio.write(pin_relay, gpio.HIGH)

wifi.setmode(wifi.STATION)
wifi.sta.config("SSID", "password")
wifi.sta.connect()
wifi.sta.setip({ip="192.168.1.200",netmask="255.255.255.0",gateway="192.168.1.1"})
print("ESP8266 mode is: " .. wifi.getmode())
print("The module MAC address is: " .. wifi.ap.getmac())
print("Config done, IP is "..wifi.sta.getip())

srv=net.createServer(net.UDP)
srv:on("receive", function(srv, pl)
   if pl=="switch" then 
    if state == 0 then
        gpio.write(pin_relay,gpio.LOW)
        state = 1
    elseif state == 1 then
        gpio.write(pin_relay,gpio.HIGH)
        state = 0
    end
   end
end)
srv:listen(port)

Answer 1

It turns out that my wireless router is the problem.. when i tried a different router, it runs no problem until now. Been running for 3 days now :)