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Xiaobian to share with you how to use tcpdump in linux, I believe most people still do not know how, so share this article for everyone's reference, I hope you have a lot of harvest after reading this article, let's go to understand it together!

tcpdump

When analyzing the fastcgi program, we use this command to check the tcp package:

[root@localhost ~]# tcpdump -i lo -s 1500 port 9000tcpdump: verbose output suppressed, use -v or -vv for full protocol decodelistening on lo, link-type EN10MB (Ethernet), capture size 1500 bytes15:23:16.901004 IP localhost.localdomain.50867 > localhost.localdomain.9000: S 3482201970:3482201970(0) win 32767 15:23:16.901025 IP localhost.localdomain.9000 > localhost.localdomain.50867: S 3473410857:3473410857(0) ack 3482201971 win 32767 15:23:16.901039 IP localhost.localdomain.50867 > localhost.localdomain.9000: . ack 1 win 256 15:23:16.901150 IP localhost.localdomain.50867 > localhost.localdomain.9000: P 1:1377(1376) ack 1 win 256 15:23:16.901170 IP localhost.localdomain.9000 > localhost.localdomain.50867: . ack 1377 win 256 15:23:16.901214 IP localhost.localdomain.9000 > localhost.localdomain.50867: P 1:97(96) ack 1377 win 256 15:23:16.901222 IP localhost.localdomain.50867 > localhost.localdomain.9000: . ack 97 win 256 15:23:16.901236 IP localhost.localdomain.9000 > localhost.localdomain.50867: F 97:97(0) ack 1377 win 256 15:23:16.901822 IP localhost.localdomain.50867 > localhost.localdomain.9000: F 1377:1377(0) ack 98 win 256 15:23:16.901836 IP localhost.localdomain.9000 > localhost.localdomain.50867: . ack 1378 win 256

We can find that port 9000 actively closes the connection through this command, which means that maintaining the connection at the other end has no effect.

That's all for "how to use tcpdump in linux." Thanks for reading! I believe that everyone has a certain understanding, hope to share the content to help everyone, if you still want to learn more knowledge, welcome to pay attention to the industry information channel!

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