Help: I can't run MFTP and Ping

[zxg60481@mail1.sjtu.edu.cn (Zhu xg)]

Hi,
   I downloaded the MFTP source code and modified the files described in
"mftp_readme.html". I got the wrong result when I ran the demo
"mftp_demo.tcl". The result is

invalid command name "Agent/MFTP/Snd"
    while executing
"Agent/MFTP/Snd create _o90 "
    invoked from within
"catch "$className create $o $args" msg"
    (procedure "new" line 3)
    invoked from within
"new Agent/MFTP/Snd"
    (file "mftp_demo.tcl" line 74)

  When I tested the Ping programs described in NS Tutorial written by Marc
Greis, the result is similar. Modifications are follow the instruction in
the Tutorial.

invalid command name "Agent/Ping"
     while executing
"Agent/Ping instproc recv {from rtt} {
        $self instvar node_
        puts "node [$node_ id] received ping answer from \
              $from with round-trip-tim..."
    (file "ping.tcl" line 27)

  Are there any modifications I didn't modify. Who can help me? My
environment is ns-2.1b3 in Linux.
  Thanks.
             Zhu Xiaogang