attempt to call field 'AddNetworkString' (a nil value)

[xpuska]

So i'm trying to make a simple exam system for my server,but when i tryin to addnetworkstring it returns a nil value.
P.s i'm doing it on serverside
Here's the code:
sv:
util.AddNetworkString("passedexam")
util.AddNetworkString("failedexam")
util.AddNetworkString("congr_exam")
util.AddNetworkString("set_lvl_2")

net.Receive("passedexam", teleport_from_spawn)

function teleport_from_spawn(len, ply)
ply:SetPos(Vector(-10645.467773, 8759.331055, 49.031250), Vector( 0, 0, 0 ))
net.Start("congr_exam")
net.Send(ply)
end

net.Receive("set_lvl_2", function(len, ply)
game.ConsoleCommand("ulx setlevel "..ply:Nick().." 4")
end)
cl:
function examframe()
local frame = vgui.Create("DFrame")
frame:SetSize(400, 300)
frame:Center()
frame:SetVisible(true)
frame:MakePopup()

local quest1 = vgui.Create("DLabel", frame)
quest1:SetSize(100,25)
quest1:SetPos(10,25)
quest1:SetText("Question1")

local answr1 = vgui.Create("DComboBox", frame)
answr1:SetSize(100,45)
answr1:SetPos(10,45)
answr1:SetValue("Your Answer")
answr1:AddChoice("Answer1")
answr1:AddChoice("Answer2")
answr1:AddChoice("AnswerОтвет3")

local quest2 = vgui.Create("DLabel", frame)
quest2:SetSize(100,25)
quest2:SetPos(10,85)
quest2:SetText("Question2")

local answr2 = vgui.Create("DComboBox", frame)
answr2:SetSize(100,45)
answr2:SetPos(10,105)
answr2:SetValue("Your Answer")
answr2:AddChoice("Answer1")
answr2:AddChoice("Answer2")
answr2:AddChoice("Answer3")

local finishbutton = vgui.Create("DButton", frame)
finishbutton:SetSize(100,45)
finishbutton:SetPos(150,250)
finishbutton.DoClick = function(ply)
if answr1:GetSelectedID() == 1 and answr2:GetSelectedID() == 3 then
net.Start("passedexam")
net.SendToServer()
print(answr1:GetSelectedID())
print(answr2:GetSelectedID())
else
notification.AddLegacy("You failed the exam", NOTIFY_HINT, 4)
end
frame:Close()
end

end

hook.Add( 'OnPlayerChat', 'test_cmd', function( ply, txt, team, dead )
if txt == '!noobtest' and ply == LocalPlayer() and ply:getDarkRPVar("level") == 0 then
vopros()
else
notification.AddLegacy("You don't need to do that", NOTIFY_HINT, 6)
end
end )

net.Receive("congr_exam", function(len)
ChatPrint("Some cong")
notification.AddLegacy("Teleported to default spawn", NOTIFY_HINT, 5)
net.Start("set_lvl_2")
net.SendToServer()
end)

[Timbo]

hook.Add( 'OnPlayerChat', 'test_cmd', function( ply, txt, team, dead )
if txt == '!noobtest' and ply == LocalPlayer() and ply:getDarkRPVar("level") == 0 then
vopros()
else
notification.AddLegacy("You don't need to do that", NOTIFY_HINT, 6)
end
end )
what is vopros for a function? if u replace it with examframe() it will open your frame

http://prntscr.com/i3h4ok

[xpuska]

Well it opens now i guess i messed up with a code somewhere. But how to set level of user that passed exam?