ubuntu18.04 compile project error: Cannot find pcac.h

The system cannot find the solution for "pcap.h":

Install libpcap library

1. Open the website: www.tcpdump.org/ to download the libpcap-1.9.1.tar.gz (512.0KB) software package, put it into a custom installation directory, and unzip the file.
2. Enter the folder and execute:

sudo ./configure
sudo make
sudo make install

PS: When the execution of sudo ./configure reports the following error, click the link below:

configure: error: Neither flex nor lex was found.

Solve the problem of ./configure error reporting

After solving the problem, you can successfully compile by executing the three steps in 2 normally.