Tcl command server with handling eval error

command_server.tcl

# Echo_Server --
#	Open the server listening socket
#	and enter the Tcl event loop
#
# Arguments:
#	port	The server's port number

proc Echo_Server {port} {
    global terminate
    set s [socket -server EchoAccept $port]
    vwait terminate
    exit
}

# Echo_Accept --
#	Accept a connection from a new client.
#	This is called after a new socket connection
#	has been created by Tcl.
#
# Arguments:
#	sock	The new socket connection to the client
#	addr	The client's IP address
#	port	The client's port number

proc EchoAccept {sock addr port} {
    global echo

    # Record the client's information

    puts "Accept $sock from $addr port $port"
    set echo(addr,$sock) [list $addr $port]

    # Ensure that each "puts" by the server
    # results in a network transmission

    fconfigure $sock -buffering line

    # Set up a callback for when the client sends data

    fileevent $sock readable [list Echo $sock]
}

# Echo --
#	This procedure is called when the server
#	can read data from the client
#
# Arguments:
#	sock	The socket connection to the client

proc Echo {sock} {
    global echo
    global terminate
    
    # Check end of file or abnormal connection drop,
    # then echo data back to the client.

    if {[eof $sock] || [catch {gets $sock line}]} {
	CloseSocket $sock
    } else {
        puts $sock $line
        if {$line eq "terminate"} {
	    CloseSocket $sock
            set terminate 1
        } else {
	    puts $line
	    if { [ catch { set result [ eval $line ] } ] } {
	        puts $sock "eval error"
            } else {
	        puts $sock $result
            }
	}
    }
}

proc CloseSocket {sock} {
    global echo
    close $sock
    puts "Close $echo(addr,$sock)"
    unset echo(addr,$sock)
}

Echo_Server 16384