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How can I Write a sniffer program in System Programming

Hi guys can you help me How can I build a sniffer program.

a generic google on sniffer c program

I did not specifically search for rs232 sniffing, network sniffing or whatever, only tried to find some c-code.

I am talking about Network Sniffing

Use libcap. It uses Berkeley packet filter

Code:

#include <pcap.h>

#include <net/if.h>

#include <netinet/in.h>

Use pcap_lookupdev to choose the interface
Use pcap_open_live to get a packet capture descriptor
Use pcap_lookupnet to get network information from interface
Use pcap_compile to transform your filter text into a BPF filter
Use pcap_setfilter to apply the filter
Use pcap_loop to set a function that will be called on every packet matching the filter
Compile with -lpcap

man pcap will give you more information

The other solution would be to redo everything but I don't think its interesting to reinvent the wheel..

Have fun