Attached you find a text file which is showing the entire TCP
communication with the server in question.

Wireshark display filter:

  ip.addr == 201.77.194.91 && tcp.port == 80

What can be seen here:

1. A POST request is issued.

2. No communication for 40s. (= CURLOPT_TIMEOUT, CURLOPT_CONNECTTIMEOUT)

3. There is brief communication. I assume that cURL tells the server to
  give up (FIN, ACK), and the server responds quickly (ACK).

3. No communication for 159s.

3. The server responds with RST, ACK.

So far I saw the problem only twice today, and both times it was the
same pattern:

1. query: no problem

2. long pause of 30 to 60 min

3. another query: timeout hit

Background information: This is web-scraping that I am implementing for
a customer. While my customer is in contact with the airline company
that runs the servers, I doubt that they will change anything especially
for us. According to my customer, they do not even provide an API (which
would make things much more straight forward). So, there is no choice
other than to work around the problem client-side.

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