Practical Programming in Tcl & Tk, Third Edition

The Echo Service

Example 17-3 The echo service.

proc Echo_Server {port} { global echo set echo(main) [socket -server EchoAccept $port] } proc EchoAccept {sock addr port} { global echo puts "Accept $sock from $addr port $port" set echo(addr,$sock) [list $addr $port] fconfigure $sock -buffering line fileevent $sock readable [list Echo $sock] } proc Echo {sock} { global echo if {[eof $sock] || [catch {gets $sock line}]} { # end of file or abnormal connection drop close $sock puts "Close $echo(addr,$sock)" unset echo(addr,$sock) } else { if {[string compare $line "quit"] == 0} { # Prevent new connections. # Existing connections stay open. close $echo(main) } puts $sock $line } }

The echo server accepts connections from clients. It reads data from ...