libpcaps

Libpcap is a portable open-source library written in C that provides a uniform interface for capturing network traffic. It enables applications to capture packets from live network interfaces or to read from saved capture files (pcap files). By encapsulating platform-specific capture mechanisms, libpcap offers a consistent programming model across a wide range of operating systems.

Libpcap is the foundation for many network analysis tools, most notably tcpdump, and is widely used by packet analyzers, intrusion detection systems, and network measurement utilities. It is the de facto capture API on Unix-like systems and is available on Windows platforms through ports such as WinPcap and Npcap. The library and its accompanying tools are distributed as free, open-source software under a BSD-like license.

The API supports live capture through pcap_open_live, offline capture via pcap_open_offline, and packet iteration with pcap_loop or pcap_next_ex. It includes filtering capabilities through the Berkeley Packet Filter (BPF) language, with functions such as pcap_compile and pcap_setfilter to apply filters. Additional features include statistics gathering, datalink type discovery, and dump/file writing support via pcap_dumper.