Free networking two computers software for linux

Understanding computer networks without performing practical experiments is really difficult, not to say it is almost impossible. Unfortunately, setting up a networking lab can be very expensive.

Netkit has been conceived as an environment for setting up and performing networking experiments at low cost and with little effort. It allows to "create" several virtual network devices (full-fledged routers, switches, computers, etc.) that can be easily interconnected in order to form a network on a single PC. Networking equipments are virtual but feature many of the characteristics of the real ones, including the configuration interface.

Netkit exploits open source software (mostly licensed under GPL) and is heavily based on the User Mode Linux (UML) variant of the linux kernel. The purpose of this project is to solve many of the difficulties and technicalities that a user could have in using UML for networking. We offer the users an easy-to-use-and-install package, which at the same time implements effective network emulation. Further, we provide a corpus of teaching material that can be used for courses at different levels.

Netkit has been conceived for doing networking experiments at low cost. Several fully fledged routers, switches, and computers can be easily "created" and interconnected on a single pc.
Such networking equipments are virtual but can be operated with many of the features of the real ones.
Netkit exploits open source software (mostly licensed under GPL) and is heavily based on User Mode Linux (UML). The purpose of our efforts is to solve many of the difficulties and technicalities that a user could have in using UML for networking. Namely, we offer to the users an easy to use and to install package.
Enhancements:
- Improved checks for the presence of terminal emulator applications (both in check_configuration.sh and in the Netkit scripts).
- Fixed a bug inside vcrash and vclean (wrong signal spec when killing processes broke both vcrash and vclean).
- Placed a workaround to avoid early hangs of the port-helper process when booting virtual machines.
- Removed some minor warnings issued by vstart and vclean.
- Fixed a small bug in the output of vlist.

Computer Breaker project is a network testing tool for services vulnerabilities.

Computer Breaker is a network testing tool that allows networking administrators to test if a computer is vulnerable to malicious attacks.

Using the Nessus scanner, computer-breaker scans the remote host and automatically exploits its vulnerabilities.

Remote Monitoring Agent (RMA in short) is an auxiliary application for HostMonitor. Enterprise license for Advanced Host Monitor already includes license for 10 installations of the agent. Holders of a Lite, Standard or Professional licenses may buy an additional license for Remote Monitoring Agent separately.
HostMonitor 4.0+ can monitor remote networks using Remote Monitoring Agents (RMA). RMA is small application that accepts requests from HostMonitor, performs test and provides information about test result back to HostMonitor.
Why you may need RMA? Here are just several reasons:
RMA increases security of the network. When you have to run the tests such as CPU Usage test or Performance Counters tests on a remote Windows system, HostMonitor must be able to log in to that system with administrators privileges. Instead you may now use an agent installed on that remote system. In this case HostMonitor will not have to log on to that system at all. HostMonitor needs just one TCP port to communicate with the RMA agent (by default it uses #1055 port, however you may set an agent to use any other port).
Remote Monitoring Agent is also a very useful tool when you have to monitor two (or many) separated networks (connected through Internet). In this case installing just one instance of RMA behind the firewall in network "A" will allow to monitor entire network "A" using the HostMonitor located in the network "B" with just one open TCP port.
RMA decreases the network traffic. E.g. frequent use of "File Integrity" or "Compare Files" tests in an array of remote systems may apply significant load on the network. The more and the bigger files you test the more traffic increase you get. RMA runs locally and sends only the test results to the HostMonitor thus decreasing the amount of network traffic.
Remote Monitoring Agent simplifies network administration. You no longer need to share local drives/folders to perform tests such as File Integrity, Folder/File Size, File Availability, Count Files, etc
RMA for Linux / BSD / Solaris allows you to perform tests that HostMonitor cannot perform. For example HostMonitor cannot monitor processes that are running on Linux systems. RMA can do that.
Main features:
- All traffic between Remote Monitoring Agents and HostMonitor is encrypted.
- It is possible to customize the list of enabled tests for each of the agents (e.g. living only Count Files and UNC tests only).
- You can restrict incoming TCP connections with the list of acceptable addresses.
- With RMA Manager you may configure, restart and even upgrade agent(s) remotely.

The Torque Network Library project is a robust, secure, and easy-to-use cross-platform C++ networking API designed for high performance simulations and games.
It features a UDP- based connection architecture with DoS prevention functionality, different types of data guarantee, bit stream compression, server object replication and updating, and a simple, highly space efficient RPC mechanism.
It includes a deterministic application journaling replay function for eliminating hard to find networking bugs.
Main features:
- Portable
- Powerful RPC Support
- Lightweight and efficient - not intended to be a replacement for CORBA.
- Extremely easy to use - two simple macro definitions and youre done.
- No complex wrapper classes to work with - write and call your functions as you normally would, and TNL will take care of the rest.
- Robust UDP-based notification protocol
- Supports fixed or adaptive rate data transfer.
- Arbitrary sized packet window.
- Robust connection handshaking.
- Handles packet loss/out of order delivery.
- Networked Objects
- Instantiation of objects by name or ID.
- IDs are assigned to NetGroups, so that only objects relevant to a connection can be references.
- Event Support
- Unguaranteed, guaranteed unordered, or guaranteed ordered event delivery.
- Notification to the event when it has been received or dropped by a client.
- Ghost Support
- Most-recent state information is transmitted to clienst.
- Scoping of objects to only those clients for which they are relevant - this helps prevent cheating or data sniffing and makes dramatically more effective use of available bandwidth.
- Prioritization of state updates by arbitrary criteria, such as relative velocity, team, ownership, etc.
- Extensible Protocol Architecture
- Easy to extend the protocol, for instance, to transmit player move information with every packet, or add voice support.
- See Torque for examples of additional capabilities that could be added to the protocol.

TAP provides packet reception and transmission for user-space programs. It can be viewed as a simple Ethernet device, which instead of receiving packets from a physical medium, receives them from a user-space program and instead of sending packets via physical media, writes them to the user-space program.
When a program opens /dev/tunX or /dev/tapX, driver creates and registers corresponding net device tunX or tapX. After a program closed above devices, driver will automatically delete tunXX or tapXX device and all routes corresponding to it.
This package(http://vtun.sourceforge.net/tun) contains two simple example programs that shows you how to use tun and tap devices. Both programs work like bridge between two network interfaces. br_select.c - bridge based on select system call. br_sigio.c - bridge based on async io and SIGIO signal. However the best example is VTun http://vtun.sourceforge.net
Enhancements:
- Massive Linux driver update: 2.4.x kernel support. New cloning interface, protocol indication. Statistics counting fixes.
- Solaris driver update: Correct Ethernet header substitution.
- Configure and Makefile updates. RPM package update.
- Documentation update.