Echo via Socket

Below example starts a server and waits client to send a string and echo back to client.

Server

callback function must have three parameters: socket handle, address, and port.

proc callback {sock addr port} {
	fconfigure $sock -translation lf -buffering line
	fileevent $sock readable [list echo $sock]
}

echo fuction reads from socket and puts the line back.

proc echo {sock} {
	global var
	if {[eof $sock] || [catch {gets $sock line}]} {
		close $sock; set var done
	} else {
		puts $sock "$line"; puts "show echo: $line"
	}
}

init socket and wait done.

set port 2800
set sh [socket -server callback $port]
puts "socket is ready"
vwait var; close $sh

Client

open a client socket in localhost.

set host localhost; set port 2800
set s [socket $host $port]
fconfigure $s -buffering line; puts $s $host