![]() You're feeling generous, mail me a check. No GPLs, Berkeley copyrights or any of that nonsense. It will be useful, with no restrictions except giving credit where it is due. It is freely given away to the Internet community in the hope that Netcat is entirely my own creation, although plenty of other code was used asĮxamples. "Maximize-Throughput", "Maximize-Reliability", or b allow UDP broadcasts -r randomize local and remote ports -s addr local source address -t enable telnet negotiation -u UDP mode -v verbose -w secs timeout for connects and final net reads -C Send CRLF as line-ending -z zero-I/O mode -T type set TOS flag (type may be one of "Minimize-Delay", ) -q seconds after EOF on stdin, wait the specified number of seconds and then quit. 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 g gateway source-routing hop point, up to 8 -G num source-routing pointer: 4, 8, 12. e filename specify filename to exec after connect (use with caution). You don't have a working /bin/sh (Note that POSIX-conformant system must String is passed to /bin/sh -c for execution. ![]() OPTIONS ¶ -c string specify shell commands to exec after connect (use with caution). Smaller and faster than telnet, and has many other advantages. Netcat doesn't have any of these limitations, is much Never modify any of the real data in transit unless you *really* want it to.Īnd of course telnet is incapable of listening for inbound connections, or Netcat keeps such things religiously separated from its *output* and will Telnet also emits some of its diagnostic messages to standard output, where Interpreted as telnet options and are thus removed from the data stream. TelnetĪlso will not transfer arbitrary binary data, because certain characters are Main reason netcat stays running until the *network* side closes. The "standard input EOF" problem, so one must introduce calculatedĭelays in driving scripts to allow network output to finish. You may be asking "why not just use telnet to connect toĪrbitrary ports?" Valid question, and here are some reasons. Sending large amounts of data that way, but it's still a useful capability UDP, as the "U" implies, gives less reliableĭata transmission than TCP connections and some systems may have trouble "udp telnet-like" application you always wanted for testing your In either mode, shutdown can beįorced after a configurable time of inactivity on the network side.Īnd it can do this via UDP too, so netcat is possibly the "client" or "server" mode - it still shovels data backĪnd forth until there isn't any more left. With minor limitations, netcat doesn't really care if it runs in Netcat can also function as a server, by listening for inboundĬonnections on arbitrary ports and then doing the same reading and writing. Note that this behavior isĭifferent from most other applications which shut everything down and exitĪfter an end-of-file on the standard input. Network side of the connection shuts down. Is then sent to the host, and anything that comes back across the connection In the simplest usage, "nc host port" creates a TCPĬonnection to the given port on the given target host. Supplied long ago as another one of those cryptic but standard Unix tools. ![]() Netcat, or "nc" as the actual program is named, should have been At the same time, it is a feature-rich networkĭebugging and exploration tool, since it can create almost any kind ofĬonnection you would need and has several interesting built-in capabilities. Reliable "back-end" tool that can be used directly or easily drivenīy other programs and scripts. Network connections, using TCP or UDP protocol. nc -l -p port DESCRIPTION ¶ netcat is a simple unix utility which reads and writes data across
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