10 More Discussions You Might Find Interesting
1. UNIX for Advanced & Expert Users
Hi everybody,
I am running a program on a supercomputer via my personal computer through a ssh connection. My program take more than a day to run, so when I left work with my PC I stop the connection with the supercomputer and the program stop.
I am wondering if someone know how I can manage... (2 Replies)
Discussion started by: TomTomGre
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2. Debian
I have two computers running Debian 6.0 and one running Solaris 2.6 on a private network. The Debian computers can ftp to the Solaris computer but if a Debian computer is the destination the ftp connection is refused. I assume this is some security feature of Debian. What can I do to allow... (2 Replies)
Discussion started by: snorkack59
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3. UNIX for Advanced & Expert Users
Hi- While trying ftp from AIX to Windows im getting below error. Can anyone share ur views on this topic.
root@AB101# ftp -n 10.192.168.68
ftp: connect: A remote host refused an attempted connect operation.
ftp>
Thanks. (3 Replies)
Discussion started by: yanis
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4. UNIX and Linux Applications
I dont' what happened with my servers (test servers only) but I just noticed that suddenly I cannot up the domain anymore (Sun Java System Application Server 9.1_01).
a. server.log
org.postgresql.util.PSQLException: Connection refused. Check that the hostname and port are correct and that the... (1 Reply)
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5. Solaris
Hi everyone,
I am hoping anyone of you could help me in this weird problem we have in 1 of our Solaris 10 servers. Lately, we have been having some ftp problems in this server. Though it can ping any server within the network, it seems that it can only ftp to a select few. For most servers, the... (4 Replies)
Discussion started by: labdakos
4 Replies
6. Programming
OS : Solaris sparc
In c program After socket created when I do Connect() it results "Connection refused", but the system is online and I am able to do telnet, ping everything, but it says connection refused.
What would need to correct ? (6 Replies)
Discussion started by: satish@123
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7. UNIX for Dummies Questions & Answers
Hi Everyone,
Good day.
Scenario:
2 unix servers -- A (SunOS) and B (AIX)
I have an ftp script to sftp 30 files from A to B which happen almost instantaneously i.e 30 sftp's happen at the same time.
Some of these sftp's fail with the following error:
ssh_exchange_identification: Connection... (1 Reply)
Discussion started by: jeevan_fimare
1 Replies
8. IP Networking
Hi there,
Anything will help.
I have running server on computer and want to connect from some clients.
Server:
memset(&hints, 0, sizeof(hints));
hints.ai_family = domain;
hints.ai_socktype = SOCK_STREAM;
error = getaddrinfo("localhost", "8300", &hints, &res0);
if (error)
{
... (1 Reply)
Discussion started by: Dudu1984
1 Replies
9. UNIX for Dummies Questions & Answers
Hello
I need to close some ports on a box Solaris 8, which command I need to use.
Thanks for your replies (2 Replies)
Discussion started by: lo-lp-kl
2 Replies
10. SCO
I installed Openserver 5.0.7 and I cannot telnet to the localhost and I can't telnet from my old SCO 3.2.42 to the new SCO machine but I can ping the new machine and it will telnet to the old machine. (2 Replies)
Discussion started by: printrick
2 Replies
NC(1) General Commands Manual NC(1)
NAME
nc - TCP/IP swiss army knife
SYNOPSIS
nc [-options] hostname port[s] [ports] ...
nc -l -p port [-options] [hostname] [port]
DESCRIPTION
netcat is a simple unix utility which reads and writes data across network connections, using TCP or UDP protocol. It is designed to be a
reliable "back-end" tool that can be used directly or easily driven by other programs and scripts. At the same time, it is a feature-rich
network debugging and exploration tool, since it can create almost any kind of connection you would need and has several interesting built-
in capabilities. Netcat, or "nc" as the actual program is named, should have been supplied long ago as another one of those cryptic but
standard Unix tools.
In the simplest usage, "nc host port" creates a TCP connection to the given port on the given target host. Your standard input is then
sent to the host, and anything that comes back across the connection is sent to your standard output. This continues indefinitely, until
the network side of the connection shuts down. Note that this behavior is different from most other applications which shut everything
down and exit after an end-of-file on the standard input.
Netcat can also function as a server, by listening for inbound connections on arbitrary ports and then doing the same reading and writing.
With minor limitations, netcat doesn't really care if it runs in "client" or "server" mode -- it still shovels data back and forth until
there isn't any more left. In either mode, shutdown can be forced after a configurable time of inactivity on the network side.
And it can do this via UDP too, so netcat is possibly the "udp telnet-like" application you always wanted for testing your UDP-mode
servers. UDP, as the "U" implies, gives less reliable data transmission than TCP connections and some systems may have trouble sending
large amounts of data that way, but it's still a useful capability to have.
You may be asking "why not just use telnet to connect to arbitrary ports?" Valid question, and here are some reasons. Telnet has the
"standard input EOF" problem, so one must introduce calculated delays in driving scripts to allow network output to finish. This is the
main reason netcat stays running until the *network* side closes. Telnet also will not transfer arbitrary binary data, because certain
characters are interpreted as telnet options and are thus removed from the data stream. Telnet also emits some of its diagnostic messages
to standard output, where netcat keeps such things religiously separated from its *output* and will never modify any of the real data in
transit unless you *really* want it to. And of course telnet is incapable of listening for inbound connections, or using UDP instead.
Netcat doesn't have any of these limitations, is much smaller and faster than telnet, and has many other advantages.
OPTIONS
-c string specify shell commands to exec after connect (use with caution). The string is passed to /bin/sh -c for execution. See the
-e option if you don't have a working /bin/sh (Note that POSIX-conformant system must have one).
-e filename specify filename to exec after connect (use with caution). See the -c option for enhanced functionality.
-g gateway source-routing hop point[s], up to 8
-G num source-routing pointer: 4, 8, 12, ...
-h display help
-i secs delay interval for lines sent, ports scanned
-l listen mode, for inbound connects
-n numeric-only IP addresses, no DNS
-o file hex dump of traffic
-p port local port number (port numbers can be individual or ranges: lo-hi [inclusive])
-q seconds after EOF on stdin, wait the specified number of seconds and then quit. If seconds is negative, wait forever.
-b allow UDP broadcasts
-r randomize local and remote ports
-s addr local source address
-t enable telnet negotiation
-u UDP mode
-v verbose [use twice to be more verbose]
-w secs timeout for connects and final net reads
-z zero-I/O mode [used for scanning]
-T type set TOS flag (type may be one of "Minimize-Delay", "Maximize-Throughput", "Maximize-Reliability", or "Minimize-Cost".)
COPYRIGHT
Netcat is entirely my own creation, although plenty of other code was used as examples. It is freely given away to the Internet community
in the hope that it will be useful, with no restrictions except giving credit where it is due. No GPLs, Berkeley copyrights or any of that
nonsense. The author assumes NO responsibility for how anyone uses it. If netcat makes you rich somehow and you're feeling generous, mail
me a check. If you are affiliated in any way with Microsoft Network, get a life. Always ski in control. Comments, questions, and patches
to hobbit@avian.org.
NOTES
Some port names in /etc/services contain hyphens -- netcat currently will not correctly parse those unless you escape the hyphens with
backslashes (e.g. "netcat localhost 'ftp-data'").
BUGS
Efforts have been made to have netcat "do the right thing" in all its various modes. If you believe that it is doing the wrong thing under
whatever circumstances, please notify me and tell me how you think it should behave. If netcat is not able to do some task you think up,
minor tweaks to the code will probably fix that. It provides a basic and easily-modified template for writing other network applications,
and I certainly encourage people to make custom mods and send in any improvements they make to it. Continued feedback from the Internet
community is always welcome!
EXAMPLES
For several netcat recipes, please see /usr/share/doc/netcat/README.gz and /usr/share/doc/netcat/README.Debian.gz.
AUTHOR
This manual page was written by Joey Hess <joeyh@debian.org> and Robert Woodcock <rcw@debian.org>, cribbing heavily from Netcat's README
file.
Netcat was written by a guy we know as the Hobbit <hobbit@avian.org>.
NC(1)