I have php 4.3.3 and dbg on my RH 7.3 box.
usig telnet a.b.c.d 7869 reports

Could not open a connection to host on port 7869

from php.ini:
[debugger]
debugger.enabled = true
debugger.profiler_enabled = true
debugger.JIT_host = 192.168.a.b
debugger.JIT_port = 7869
debugger.hosts_allow = 192.168.a.b
debugger.hosts_deny = ALL


What is wrong and how correct it?

Thanks Mike

Please read the instructions carefully. There is not stated that dbg installed on the server is available via telnet. Telnet may be used for checking if connection to your client machine is possible from the server, not vice versa.
When you check connection by telnet, please make sure the DbgListener on the client computer is running.