Free tcp connections software for linux

TCPreen is a simple tool to monitor and analyze data transmitted between clients and servers through connection-oriented streams data such as a TCP sessions; it supports TCP over either IPv4 or IPv6. This tool focuses on the data stream (software/socket layer), not on the lower level transmission protocol as packet sniffers do.

TCPreen listens on a TCP port and wait for incoming connections to come in. Then, it forwards data sent by the connecting client to another server port (possibly on another computer) and forwards server responses back to the client.

TCPreen can display data on your console in real-time and/or save it to log files for later reference. Various display formats are available.

While it was originally meant to help developers reverse-engineer TCP-based protocols, it can also be very useful to debug network server or client software or for a system administrator to monitor a TCP service.

Cutter is an TCP/IP Connection cutting on Linux Firewalls and Routers.

Cutter is an open source program that uses the FIN-ACK-RST packet technique described above to abort TCP/IP connections routed over the firewall or router on which it is run. It can be called using one of the following four syntaxes.

cutter ip-address

Example: "cutter 10.10.0.45"

Cuts all connections passing through the firewall between any ports on the specified ip-address (either a "private" or "public" address) and any other hosts. This can be used to close down all incoming connections to a particular server, all outgoing connections from a particular client or all outgoing connections to a server.

cutter ip-address port

Example: "cutter 200.1.2.3 80"

Cuts all connections to or from the specified ip-address/port pair. This allows the user to be a little more specific than the previous example and allows targetting of specific services on specific hosts.

cutter ip-address-1 port-1 ip-address-2

Example "cutter 200.1.2.3 22 10.10.0.45"

Cuts all connections between ip-address-2 and ip-address-1/port-1. This allows the user to cut connections between a specified "client" and a particular service on a specified host. Our example closes host 10.10.0.45s SSH connection to server 200.1.2.3.

cutter ip-address-1 port-1 ip-address-2 port-2

Example: "cutter 200.1.2.3 22 10.10.0.45 32451"

Cuts the specific connection between the two ip/port number pairs given.

IMPORTANT WARNING

Cutter has been designed for use as a administrators tool for Linux firewalls. Its use (as is, or modified) for any other purpose is not sanctioned by the author. So - do not use this tool as a parachute, or to dry your cat, chill meat, answer your phone, drive you car, teach your kids to read or attack other peoples computer systems or networks.

This software has been designed for "legal" and "appropriate" use by network security administrators and the like. It has been written as part of a larger Linux firewall project, targetting at controlling traffic from peer-to-peer software such as Kazaa, iMesh and others into and out of a private network. It is not designed as a tool for malicious use and the author in no way sanctions such use.

Users of the software should be aware that its actions are easily detectable using a number of readily available network monitoring tools, and it makes no attempt to disguise its actions. Malicious use of "cutter" could result in a jail sentance in a number of countries around the world.

TCPWatch is a utility written in Python that lets you monitor forwarded TCP connections or HTTP proxy connections.
It displays the sessions in a window with a history of past connections. It is useful for developing and debugging protocol implementations and web services.
Enhancements:
- Made compatible with versions of tcl that have threads enabled.
- Log file numbers are now sequential.
- "user@host" is now accepted as a destination hostname (the user name is ignored).

Program Guard allows the user of a Linux workstation to specify which application programs that are allowed TCP/IP connections to the Internet (Internet addresses are defined as any IP address not in the range of 10.0.0.0/24 or 192.168.0.0/16).

The application program names can be specified by listing them in a file (Static Mode) by querying the user (Query Mode). In Query Mode, when a program that is unknown to Program Guard attempts to access an Internet IP address, Program Guard displays the Program Guard Dialog Box.

In addition to providing connection information, this dialog box gives the workstation user the option of allowing the program to access the Internet or to be blocked from accessing the Internet. This can be done either for the current instance of the program or for this and all future instances of the program (Make Persistent checkbox).

Currently, the program names that are allowed or denied Internet access apply to all users of the workstation rather than on a per user basis. For example, if Program Guard is running in Query Mode and user A invokes a program previously blocked from Internet access by user B, the program will be blocked from Internet access for User A as well.

Connections blocked by Program Guard are logged to the Program Guard log file pgrd.log. It is located in the /var/log/pgrd directory. If desired, Program Guard can be configured to log all Internet connection attempts rather than just those that have been blocked.

Program Guard was tested on Fedora Core 1 and Fedora Core 3 on single processor 32 bit X86 Intel processors. It has not been tested on other distributions or on multi-processor machines. While it works on Fedora Core 1, it will not build on a standard Linux 2.4.x kernel due to task_struct definitions that were not made until Linux 2.6. If there is enough interest, a version that runs under a standard Linux 2.4 kernel may be made available.

To run in Query Mode, Gnome 2.x and Glade 2.x are required. There are no prerequisites for Static Mode.

Installation:

Program Guard consists of three components: a kernel module; a daemon; and a Gnome GUI user interface component. All files needed to build the components are in the pgrd.tgz file. An installation shell script install-pgrd is provided for Fedora distributions.

It will build/install (or remove) the kernel module and daemon as well as configure them to be started automatically when the system is booted. To invoke it, type install-pgrd < install | remove >. This script may or may not be useable as is for other Linux distributions.

If you modify the install script, please note that the module, daemon and various support files must be installed in the /opt/pgrd directory for Program Guard to work properly (this is already handled when using the install script as provided). To run in Query Mode, each user must be configured by invoking the install-pgrd_user < username > script. And by going to the Preferences->More Preferences->Sessions selection in the Fedora Main Menu and adding pgrdgui to the Startup Programs tab.

Program Guard will be started the next time the machine is rebooted. If you do not wish to reboot, you may start Program Guard manually as described below in Manual Starting And Stopping. Note: If starting manually and using Query Mode, once the daemon and kernel module are started, make sure that you log out and log back in.

prtunnel is a program that can tunnel TCP/IP connections in a variety of ways, including through HTTP and SOCKS5 proxy servers. Some if its possible uses include:
- Tunneling TCP connections from client programs to a remote server through an HTTP or SOCKS5 proxy (useful if youre behind such a proxy and want to use a program that doesnt have native proxy support)
- Tunneling TCP connections from SOCKS-capable client programs through an HTTP or SOCKS5 proxy
- Tunneling TCP connections from an IPv4 client program to an IPv6 server and vice-versa
- Forwarding TCP connections
- Running as a simple SOCKS proxy server
prtunnel project was developed and used under Linux and BSD-based operating systems.
Enhancements:
- A bug that would cause malloc(0) to be called in some situations (which could cause problems on some systems) has been fixed.
- The server timeout, if specified, is now set before the proxy server successfully connects to the remote server, which will prevent the program from hanging if the proxy does not respond to the client.

Network Communicator is a simple script for sending and receiving data over TCP/UDP connections.
It can be useful for testing firewall configurations, routing tables, and similar things.
I had originally written two scripts for testing TCP only: a talker and a listener. Upon failure to properly modify them to support UDP only, I made Netcom. It allows the sending and receiving of TCP or UDP data to arbitrary IPs/Ports and optional from/to files.
Im sure there are already tools like this out there like netcat, but wasnt able to get netcat working properly for UDP also. Either way, here you go and enjoy!
Launch Netcom with no options to view the usage.
Enhancements:
- A complete re-write to support arbitrary source/destination and port forwarding (not tunneling).

conn-close gives us possibility to get rid of entries in ip_conntrack about ESTABLISHED TCP connections that goes through our server.

conn-close script uses hping2 to send spoofed RST packets which will fool conntrack and cause specified connections to be considered by conntrack as closed (now these connections will be in ip_conntrack in CLOSE state), even though RST packets will be more likely discarded by destination host.

Information about connections is read of course from /proc/net/ip_conntrack.

Idea was taken from script seen somewhere on the internet.