Packet Sniffing and Spoofing Packet Sniffing and Spoofing Copyright 2017 Wenliang Du, All rights reserved. 15.1. In the pcap-based sniffer program shown in Listing C.4 (C is the chapter number of the Packet Sniffing and Spoofing chapter, its actual value depends on which version of the book you are using), we added a check to see whether handle is NULL or not. When running this program, we get an error message, saying "NULL: No such device". What is the cause of the problem? handle = pcap_open_live ("eth1", BUFSIZ, 1, 1000, errbuf); if (handle == NULL) { perror ("NULL"); } Error message: NULL: No such device 15.2. In the pcap-based sniffer program shown in Listing C.4 (C is the chapter number of the Packet Sniffing and Spoofing chapter: its actual value depends on which version of the book you are using), we replace Line (1) with the following line. After that, when we