A RealTek Application Using our own device-driver and a standard networking protocol to discover the ‘active’ workstations

Our ‘rxplustx.c’ driver open read write my_fops ioctl my_ioctl() my_open() my_read() my_write() my_release() my_isr() init_module() cleanup_module() release

Our ‘arpquery.cpp’ program Opens device-file Gets netaddress then forks Installs a signal-handler While-loop receives ARP replies until signaled parent-process child-process For-loop transmits ARP request to all stations on local network then signals parent and exits

ARP request AB CDE request Station ‘A’ wants to know the Ethernet Address for station ‘B’ So ‘A’ broadcasts an ARP request-packet to all other stations

ARP reply AB CDE reply Station ‘B’ recognizes that the request is for its Ethernet Address. So ‘B’ replies directly to ‘A’, and other stations ignore the request.

Format for ARP Frames Source MAC address 0x0806 PTYPE 0x0800 HLEN 0x06 PLEN 0x04 ARP command Source hardware address Source protocol address Destination hardware address Destination protocol address Destination MAC address HTYPE 0x0001 Legend: ARP commands (0x0001=request, 0x0002=reply)

‘roomview.cpp’

Terminal ‘line graphics’ Most text-mode terminals can draw ‘boxes’ by using an ‘alternate character set’ which includes the so-called ‘line graphic’ glyphs: Upper-Left: ┌ Upper-Right: ┐ Horizontal-bar: ─Vertical-bar: │ Lower-left: └Lower-right: ┘ ┌───────────────┐ └───────────────┘

Uniform terminal interface Because terminal hardware may differ, we need a standard software interface to get the same desired effects on all platforms UNIX programming environments offer a long-established mechanism for doing this Need this header-file: #include Need linkage with ‘ncurses’ function-library

How ‘terminfo’ is used Initialize with the ‘setupterm()’ function Extract your terminal’s parameters (e.g., numbers or special control-strings) using the functions ‘tigetnum()’ and ‘tigetstr()’ Parametrize control-strings with ‘tparm()’ Output these control-strings with ‘putp()’ Our ‘roomview.cpp’ demonstrates these

Line-graphic character-codes Your terminal’s mapping of the numbers for the line-graphics glyphs can be found by a string-search of terminfo’s database This is illustrated in our ‘roomview’ demo Examples: char *acsc = tigetstr( “acsc” ); charHZ = strchr( acsc, ‘q’ )[ 1 ]; charVT = strchr( scsc, ‘x’ )[ 1 ];

Special terminal effects You can enable (or disable) use of glyphs from the terminal’s alternate character set, by using special control-sequences: ‘smacs’ and ‘rmacs’ You can put the cursor where you want it, by outputting a special control-sequence: ‘cup’ You can draw characters in ‘reverse-video’, by outputting a special control-sequence: ‘rev’ You can draw characters in ‘normal’ mode, by outputting a special control-sequence: ‘sgr0’

‘roomview.cpp’

In-class exercise Combine the programming ideas used in ‘roomview.cpp’ and ‘arpquery.cpp’ so you get a view of all the Kudlick Classroom’s workstations, but with those that sent ARP reply-packets shown with ‘reverse-video’ so as to highlight their presence online