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Full Discussion: Telnet vs netcat behavior
Top Forums UNIX for Advanced & Expert Users Telnet vs netcat behavior Post 302910336 by ckmehta on Wednesday 23rd of July 2014 04:27:22 PM
Old 07-23-2014
Telnet vs netcat behavior

Currently I run a number of network tests using netcat that checks for an open port on a remote IP-address, using this syntax:
Code:
netcat -v -w 5 -z 107.249.95.5 4488

For some reason, the netcat command above is hanging (although others work fine), but a telnet is showing a valid connection like below:
Code:
%  telnet 107.249.95.5 4488
Trying 107.249.95.5...
Connected to 107.249.95.5.
Escape character is '^]'.
^]

Normally with my other netcat tests, I see an immediate result like this:
aaaa.XXX.com [102.19.5.62] 22 (ssh) open
aaaa.XXX.com [102.19.5.62] 23 (telnet): Connection timed out

The only thing different/interesting about the 107.249.95.5 address is that it is over a VPN to an MQ server.

Any idea why this network test is failing, even though its obviously connectable over telnet. If it matters, I am running this on a Solaris 10 box.

Last edited by ckmehta; 07-23-2014 at 05:32 PM..
 

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PPP(1)							      General Commands Manual							    PPP(1)

NAME
pppclient, pppserver - point to point protocol SYNOPSIS
pppclient [ -d ][ -b baudrate ][ -i myipaddr ][ -p peeripaddr ][ dialdevice ] pppserver [ -d ] ndev myipaddr firstipaddr firstdev [ baud0 baud1 ... ] DESCRIPTION
The Point to Point Protocol is used to encapsulate Internet Protocol packets for transfer over serial lines or other protocol connections. Pppclient makes a connection to a PPP server and passes IP packets over the connection. If dialdevice is omitted, standard input and out- put are used as the connection. If dialdevice begins with a slash, pppclient assumes it is a file name, open(2)'s it, and uses the result as the connection. Otherwise, dialdevice is passed as the destination address to dial(2) to set up the connection. If the connection is successful, pppclient creates a pipe, pushes the IP line discipline onto it, and sets the local and remote addresses of the IP interface to myipaddr and peeripaddr. It then loops transferring packets between the pipe and the connection. If either myi- paddr or peeripaddr is omitted, pppclient requests them from the server. The options are d print debugging information. b baud rate of the serial line. p peer ip address (in case the peer asks for its ip address over IPCP). i the local ip address to be established for this connection. Pppserver treats serial lines as PPP connections, switching packets between them and the local machine. It creates a pipe for a local IP interface (address myipaddr), opens a set of serial lines, and switches packets between the local interface and the serial lines. Ndev specifies the number of serial devices to serve. The devices are named /dev/eia{firstdev} through /dev/eia{firstdev+ndev-1}. Their remote IP addresses are firstipaddr through firstipaddr+ndev-1. The default baud rate is 9600. If any arguments follow firstdev (baud0, baud1, ...), they are used as baud rates for the serial lines. The only option, -d, turns on debugging output. Both pppclient and pppserver accept all options defined in RFCs 1331 and 1332. EXAMPLES
Start up a server for serial lines /dev/eia[2-6] with remote IP addresses 131.107.1.100 through 131.107.1.103 and baud rates of 19200, 2400, 9600, 9600. The local IP address is 131.107.1.1. pppserver 4 131.107.1.1 131.107.1.100 2 19200 2400 SOURCE
/sys/src/cmd/ppp PPP(1)
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