Firewolf GPS Tracker

local CHANNEL_GPS = 65534

local function trilaterate( A, B, C )
    local a2b = B.position - A.position
    local a2c = C.position - A.position

    if math.abs( a2b:normalize():dot( a2c:normalize() ) ) > 0.999 then
        return nil
    end

    local d = a2b:length()
    local ex = a2b:normalize( )
    local i = ex:dot( a2c )
    local ey = (a2c - (ex * i)):normalize()
    local j = ey:dot( a2c )
    local ez = ex:cross( ey )

    local r1 = A.distance
    local r2 = B.distance
    local r3 = C.distance

    local x = (r1*r1 - r2*r2 + d*d) / (2*d)
    local y = (r1*r1 - r3*r3 - x*x + (x-i)*(x-i) + j*j) / (2*j)

    local result = A.position + (ex * x) + (ey * y)

    local zSquared = r1*r1 - x*x - y*y
    if zSquared > 0 then
        local z = math.sqrt( zSquared )
        local result1 = result + (ez * z)
        local result2 = result - (ez * z)

        local rounded1, rounded2 = result1:round(), result2:round()
        if rounded1.x ~= rounded2.x or rounded1.y ~= rounded2.y or rounded1.z ~= rounded2.z then
            return rounded1, rounded2
        else
            return rounded1
        end
    end
    return result:round()

end

local function narrow( p1, p2, fix )
    local dist1 = math.abs( (p1 - fix.position):length() - fix.distance )
    local dist2 = math.abs( (p2 - fix.position):length() - fix.distance )

    if math.abs(dist1 - dist2) < 0.05 then
        return p1, p2
    elseif dist1 < dist2 then
        return p1:round()
    else
        return p2:round()
    end
end

x, y, z = gps.locate()
if x == nil then
    print("Not able to get GPS location.")
    write("Computer X: ")
    x = read()
    write("Computer Y: ")
    y = read()
    write("Computer Z: ")
    z = read()
end
if ({...})[1] ~= nil then
    if ({...])[2] == "server" then
        rednet.open(({...})[1])
        while true do
            local id2, msg = rednet.receive()
            if type(msg) == "table" and msg[1] == "locatefirewolfserver" then
                rednet.broadcast("firewolf.broadcast.dns.list")
                while true do
                    local id, msg, dist = rednet.receive(1)
                    if msg == nil or os.clock() > time + 3 then
                        break
                    elseif msg == "firewolf-site:"..msg[2] then
                        rednet.send(id2,{{x,y,z},dist})
                        break
                    end
                end
            end
        end
        rednet.send(id2,{{x,y,z},dist})
    else
        print("Enter site address.")
        local site = read()
        rednet.open(({...})[1])
        local time = os.clock()
        local positions = {}
        rednet.broadcast({"locatefirewolfserver",site})
        while true do
            local id, msg, dist = rednet.receive(1)
            if msg == nil or os.clock() > time + 4 then
                break
            elseif type(msg) == "table" then
                if msg[1] == "serverlocator" then
                    table.insert(positions,{["position"] = msg[2],["distance"] = msg[3]})
                end
            end
        end
        rednet.close(({...})[1])
        local previous = trilaterate(positions[1],positions[2],positions[3])
        for i = 4, #positions do
            previous = narrow(previous,positions[i])
        end
        for i, v in pairs(previous) do
            if (type(v) == "table") then
                for k, p in pairs(v) do
                    print(p)
                end
            else
                print(v)
            end
        end
    end
end