SoftPerfect Connection Emulator
Online User Manual

Main window

The main window features three tabs, the toolbar, the main menu, an interface combo box and additional controls:

SoftPerfect Connection Emulator - Main window

Load Profile reads the configuration from an XML file previously created with the Save Profile command. The profiles are useful if you have got multiple simulation configurations each having specific settings. The Setup Filter button opens filter configuration. Unless you define a filter, the speed limit and other simulation settings apply to all packets traveling through the selected network connection. The filter allows you to apply the simulation settings to one or more IP connections, while letting all other traffic flow unrestrictedly. The Options button provides access to several user preferences that you may want to adjust.

On the Transfer Rate tab you can specify the speed limit by choosing from the predefined items or by defining your own. The Traffic Direction can also be set here; this option defines whether the incoming, outgoing or both traffic directions will be affected by transmission limits and modifications, including those on other tabs, such as packet loss, corruption or latency.

On the Latency tab you can specify whether you need latency or a delay to be applied to packets:

SoftPerfect Connection Emulator - Main window, Latency tab

Note that if you choose to process traffic in both directions, the latency will apply twice on a duplex connection: first when the packet goes out, and then again when the reply comes back in.

The difference between ‘Delay from’ and ‘Delay to’ will define latency jitter, i.e. the variation in packet delay. The greater the difference, the more significant jitter it produces.

When using variable latency, you can also specify correlation. Correlation indicates how much each current value depends on the previous one. The 0% correlation means the values are entirely random and independent of each other. Setting the correlation greater than 0% makes the sequence of values less random, therefore decreasing jitter. This chart demonstrates the effect of correlation on random latency between 100ms and 200ms:

The effect of correlation on random latency

On the Packet Loss tab you can specify the percentage or number of packets that should be lost in transit. These packets are dropped upon receiving or sending out.

The software can simulate individual and sequential packet loss. For individual packet loss, set both Sequential loss, from and Sequential loss, to to 1. Otherwise, you can specify the minimum and maximum lengths of lost packet sequences, and the software will randomly generate loss sequences within that range:

SoftPerfect Connection Emulator - Main window, Packet Loss tab

On the Duplication tab you can specify whether any packets will be duplicated upon receiving or sending out. The software merely sends out a duplicate packet twice whether to the remote computer or to the local TCP/IP stack:

SoftPerfect Connection Emulator - Main window, Duplication tab

On the Reordering tab you can specify what percentage of packets will be transmitted in a wrong order:

SoftPerfect Connection Emulator - Main window, Reordering tab

The emulator will take a packet out of the flow, then normally pass the number of packets specified as the Gap, and then insert the packet previously taken out. For example, if the gap is set to 2, the flow consists of packets A, B, C, D, E and F, and packet B was chosen as a victim, they would arrive in this order: A, C, D, B, E, F.

On the Corruption tab you can specify what packets will be corrupted. The software flips a random bit in a packet to simulate a transmission error or a faulty network device.

SoftPerfect Connection Emulator - Main window, Corruption tab

There are three ways to specify packets corruption:

  • Percentage of packets mode has victim packets chosen randomly within the specified probability.
  • Bit error rate (BER) is the number of bit errors per unit of time; for example, 2 corrupted bits per minute.
  • Bit error ratio (BER) is the number of bit errors divided by the total number of transferred bits. For example, a ratio of 10e-7 or 0.000001 means 1 bit in 1 000 000 is corrupted.

On the Capture tab you can setup logging packets to a Libpcap file for further analysis:

SoftPerfect Connection Emulator - Main window, Captuire tab

On the Port Blocking tab you can list individual ports or port ranges, packets to and from which should be dropped. To specify the protocol, prepend the port number with the letter T for TCP or U for UDP. If there is no prefix, both TCP and UDP will be dropped. This allows you to simulate a firewall or the situation where an ISP filters incoming packets.

SoftPerfect Connection Emulator - Main window, Port Blocking tab

Manipulation visualisation

The emulator features a live chart displaying manipulations performed on each packet. Each tick represents one packet that had latency, loss, duplication, reordering or corruption applied to it. Latency chart shows delays in proportion to each other: longer vertical lines represent longer delays.

SoftPerfect Connection Emulator - Live chart

Setting up a filter

In order to restrict the simulation to a specific IP stream, you can define a filter. The filter compares the protocol field, the source and destination address fields in IP packets as well as source and destination ports in TCP/UDP packets to decide pass a packet or process it. Both IP protocol versions 4 and 6 are supported:

General filter settings

If you are running one or more virtual local area networks, you can also restrict the simulation to a particular VLAN:

Filter settings: restrict the simulation to a particular VLAN


Sometimes you may need the emulator to be installed between two non-Windows network devices. In this scenario you can use the bridging feature built in to the application. To access this feature choose Tools - Bridging from the main menu:

Setting a bridge

The adapters in the bridge need to be real physical adapters (NICs) hooked up to other network hardware as shown below:

Bridging diagram

When an emulation session is in progress, SCE will be forwarding all packets arriving to the first NIC to the second NIC and vice versa. The bridge itself will be able to communicate with either side, provided its IP configuration is correct.

Active connections

SCE can display all currently established TCP connections. Choose View - Display Connections to show/hide this view. You can terminate some or all connections to stress test your application or device using the popup menu:

Display or terminate established TCP connections

Preset parameters

For convenience SCE comes with a few predefined sets of speed limits, latency and losses. These are different from profiles and are simple sets of connection parameters that represent real-world devices. For example, a 3G data connection in case of a weak signal would likely offer reduced speeds and a packet loss. If you are required to test your application or device in these conditions, you can either fine-tune everything manually, or choose one of these presets:

Preset parameters

Command-line switches

SCE supports the following command-line parameters:

consim.exe [/runtime:120] [/hide] [/quit] [config_file.xml]

If SCE is launched with a XML-file specified, it will load the specified configuration profile and begin emulation automatically. If emulation is already running, it will load the specified file and continue with the new parameters.

If the /runtime switch followed by a number of seconds is present, emulation will run for the specified number of seconds and then the application will terminate. To run the application without the user interface, specify /hide to hide the main window. To terminate emulation immediately, specify /quit to close the running instance.

End User Licence Agreement (EULA)

This software and the included documentation is copyright SoftPerfect Pty Ltd. All rights are reserved. The software may be used, installed or copied only in accordance with the terms of the licence described in the following paragraphs.


The evaluation version of the software may be freely distributed, provided that the original distribution package is not modified in any way.


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