You can also create network connections by operating at a lower level than that of open-network-stream, using make-network-process. 
| • Proc | Using make-network-process. | |
| • Options | Further control over network connections. | |
| • Features | Determining which network features work on the machine you are using. | 
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Licensed under the GNU GPL license.
    https://www.gnu.org/software/emacs/manual/html_node/elisp/Low_002dLevel-Network.html