# In TCP, what happens if I use strange hosts?

**URL:** <https://discuss.elastic.co/t/in-tcp-what-happens-if-i-use-strange-hosts/203200>\
**Category:** Beats\
**Tags:** heartbeat\
**Created:** [October 11, 2019, 9:22am UTC](https://discuss.elastic.co/t/in-tcp-what-happens-if-i-use-strange-hosts/203200 "2019-10-11T09:22:03Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![111219](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/111219/32/55161_2.png) [@111219](https://discuss.elastic.co/u/111219)\
**Post date:** [October 11, 2019, 9:22am UTC](https://discuss.elastic.co/t/in-tcp-what-happens-if-i-use-strange-hosts/203200/1 "2019-10-11T09:22:03Z")

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I am registering a host according to the form. My question is as follows:

1. What happens if I register a non-existent host such as '[aaaaabbbbbccc.com](http://aaaaabbbbbccc.com)'?

2. How long is the timeout while connecting to an unresponsive host?

3. I wonder if it performs synchronously or asynchronously for a large number of hosts.

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**Author:** ![Andrew\_Cholakian1](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/andrew_cholakian1/32/3612_2.png) [@Andrew\_Cholakian1](https://discuss.elastic.co/u/Andrew_Cholakian1)\
**Post date:** [October 14, 2019, 4:26pm UTC](https://discuss.elastic.co/t/in-tcp-what-happens-if-i-use-strange-hosts/203200/2 "2019-10-14T16:26:41Z")

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Hi! Heartbeat will return an error for non existent DNS entries. The default timeout is 16s. Heartbeat is async.

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [November 11, 2019, 4:26pm UTC](https://discuss.elastic.co/t/in-tcp-what-happens-if-i-use-strange-hosts/203200/3 "2019-11-11T16:26:49Z")

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