RedStuff chat server v0.16 by LBPHacker

-- One program from LBPHacker's RedStuff collection
-- Chat server for RS Chat client (http://pastebin.com/CcAK5mcb)
-- For ComputerCraft 1.3 or above

term.clear()
term.setCursorPos(1, 1)
termWidth, termHeight=term.getSize()
local servername=""

function trim(stringT)
    local i=1
    while (string.sub(stringT, i, i)==" ") do
        i=i+1
    end
    local startT=i
    i=string.len(stringT)
    while (string.sub(stringT, i, i)==" ") do
        i=i-1
    end
    local endT=i
    return string.sub(stringT, startT, endT)
end

function getKickUser(message)
    local i=7
    while (string.sub(message, i, i)~=" ") do
        i=i+1
    end
    return string.sub(message, 7, i-1)
end

function getKickMessage(message)
    if (string.len(getKickUser(message))+6==string.len(message)) then
        return false
    else
        return string.sub(message, string.len(getKickUser(message))+8, string.len(message))
    end
end

print("RedStuff chat server v0.16 by LBPHacker")
print("Report bugs at lbphacker@gmail.com")
print("Detecting RedNet modems...")
local modemOnSide=0
local modems=rs.getSides()
for i=1, #modems do
    if (peripheral.isPresent(modems[i]) and peripheral.getType(modems[i])=="modem") then
        modemOnSide=i
    end
end
if (modemOnSide==0) then
    print("No modems found. Place a RedNet modem one side of the computer, then restart this program.")
    print("Press any key to exit")
    os.pullEvent("key")
    return 1
end
print("Found modem on '"..modems[modemOnSide].."', opening it")
rednet.open(modems[modemOnSide])
if (fs.exists("config")) then
    local config=fs.open("config", "r")
    servername=config.readLine()
    config.close()
else
    print("First-time-running configuration")
    term.write(string.rep("-", termWidth))
    print()
    local config=fs.open("config", "w")
    term.write("Server name?: ")
    servername=read()
    print()
    config.writeLine(servername)
    config.close()
end
print()
print("Server name: '"..servername.."'")
print("Waiting for requests")

local userControl={{}, {}, {}, {}}
local arrayUcEt=0
local fromClient
local shutdown=false
local event, sender, message
local twac=false

while (not shutdown) do
    event, sender, message=os.pullEvent("rednet_message")
    message=trim(message)
    print()
    print("Received data from "..sender..": "..message)
    if (message=="/rcsping") then
        rednet.send(sender, "/rcsresp "..servername)
        print("Received ping, responding server name")
    else
        print("Searching for client in operation queue...")
        fromClient=0
        for i=1, arrayUcEt do
            if (sender==userControl[2][i] and userControl[4][i]) then
                fromClient=i
                print("Found client: "..fromClient)
            end
        end
        if (fromClient==0) then
            if (fromClient==0) then
                print("Client not found, searching for empty slot")
                for i=1, arrayUcEt do
                    if (not userControl[4][i] and fromClient==0) then
                        fromClient=i
                        print("Found empty slot: "..fromClient)
                    end
                end
            end
            if (fromClient==0) then
                print("Empty slot not found, extending operation queue")
                arrayUcEt=arrayUcEt+1
                fromClient=arrayUcEt
                print("New empty slot: "..fromClient)
            end
            if (fromClient>0) then
                print("Recording user information")
                userControl[1][fromClient]=message
                userControl[2][fromClient]=sender
                userControl[3][fromClient]=0
                userControl[4][fromClient]=true
                for i=1, arrayUcEt do
                    if (userControl[4][i]) then
                        rednet.send(userControl[2][i], "-- "..message.." joined the server")
                    end
                end
            end
        else
            twac=false
            if (message=="/exit") then
                for i=1, arrayUcEt do
                    if (userControl[4][i]) then
                        rednet.send(userControl[2][i], "-- "..userControl[1][fromClient].." left the server")
                    end
                end
                userControl[4][fromClient]=false
                twac=true
            end
            if (message=="/stop" and userControl[1][fromClient]=="admin") then
                shutdown=true
                for i=1, arrayUcEt do
                    if (userControl[4][i]) then
                        rednet.send(userControl[2][i], "/kick Server stopped")
                    end
                end
                twac=true
            end
            if (string.sub(message, 1, 5)=="/kick" and userControl[1][fromClient]=="admin") then
                shutdown=true
                if (not getKickMessage(message)) then
                    for i=1, arrayUcEt do
                        if (userControl[4][i] and userControl[1][i]==getKickUser(message)) then
                            rednet.send(userControl[2][i], "/kick Kicked by the admin")
                        end
                    end
                else
                    for i=1, arrayUcEt do
                        if (userControl[4][i] and userControl[1][i]==string.sub(message, 7, string.len(message))) then
                            rednet.send(userControl[2][i], "/kick "..getKickMessage(message))
                        end
                    end
                end
                twac=true
            end
            if (not twac) then
                for i=1, arrayUcEt do
                    rednet.send(userControl[2][i], userControl[1][fromClient]..": "..message)
                end
            end
        end
    end
end

print()
print("Shutting down...")
sleep(2)
rednet.close(modems[modemOnSide])
term.clear()
term.setCursorPos(1, 1)