Basic Modem Search

function getModem()
    if peripheral.getType("bottom") == "modem" then
        return "bottom"
    end

    if peripheral.getType("top") == "modem" then
        return "top"
    end

    if peripheral.getType("back") == "modem" then
        return "back"
    end

    if peripheral.getType("front") == "modem" then
        return "front"
    end

    if peripheral.getType("left") == "modem" then
        return "left"
    end

    if peripheral.getType("right") == "modem" then
        return "right"
    end
    return nil
end