我正在尝试检测Vagrant主机是否在本地连接到我需要访问的网络。如果不是，那么我需要并配置代理，以便可以下载构建项目所需的一些内部资源。

我如何发出给定的秒数后超时的HTTP请求，而不管其成功与否？

我希望以下代码在经过的时间内返回1或2秒：

HTTP_NETWORK_TEST_HOST = '172.16.0.1'

start1 = Time.now
begin
    http = Net::HTTP.new(HTTP_NETWORK_TEST_HOST,'80')
    http.read_timeout = 2
    http.open_timeout = 2
    response = http.start do |http|
        http.get('/')
    end
    NETWORK_Proxy_NEEDED = false
rescue Timeout::Error => e
    NETWORK_Proxy_NEEDED = true
end
finish1 = Time.now

start2 = Time.now
begin
    Timeout::timeout(1) {
        http = Net::HTTP.new(HTTP_NETWORK_TEST_HOST,'80')
        response = http.start do |http|
            http.get('/')
        end
    }
    NETWORK_Proxy_NEEDED = false
rescue
    NETWORK_Proxy_NEEDED = true
end
finish2 = Time.now


start3 = Time.now
begin
    http = Net::HTTP.start(HTTP_NETWORK_TEST_HOST,'80',{read_timeout: 5,open_timeout: 5})
    response =  http.get('/')
    NETWORK_Proxy_NEEDED = false
rescue Timeout::Error => e
    NETWORK_Proxy_NEEDED = true
end
finish3 = Time.now


puts 'time 1'
puts finish1 - start1

puts 'time 2'
puts finish2 - start2

puts 'time 3'
puts finish3 - start3

结果：

time 1
21.003133
time 2
21.012332
time 3
21.009758

al2o3-cr在freenode irc的#ruby上向我提供了答案：

https://gist.github.com/gr33n7007h/d041f4fbc08f0e065854bb180330c3ac

NETWORK_Proxy_NEEDED = 
begin
  Socket.tcp(TEST_HOST,80,connect_timeout: 1)&.close
  false
rescue Errno::ETIMEDOUT
  true
end