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FSClient is a full Windows sip client that uses Embedded FreeSWITCH and is written in WPF/.NET 4.0. It supports external/internal contact books and full headset features through a plugin system. FSClient is meant to be a full featured SIP client including standard enterprise class client functionality. It can run installed or run standalone, with the only requirement being .NET 4.0 support.




  • Unlimited simultaneous call support
  • Multiple simultaneous sip account support
  • N-Way calling with conference support (mute/deaf/kick/split/energy & volume level control on a per caller basis)
  • External / Internal contact book support (see Plugins)
  • Incoming Call Notification Tray Alerts
  • Speakerphone support and live call switching
  • Advanced headset integration (caller ID, buttons, external displays see Plugins)
  • Call stats/history with option DTMF history
  • Support for all freeswitch codecs CELT, G711(ULAW/ALAW), GSM, G722.1, SILK, Speex, BroadVoice, iLBC (minus G729 which is not yet supported in Windows)
  • DND (Do Not Disturb) Call Ignoring
  • Call Hold / Call Transfer / Muting
  • Event Socket for direct interaction with client
  • Per call volume and mic gain adjustment
  • Conference & Call recording
  • TLS / SRTP Support with certificate/subject validation
  • Direct SIP: dialing to a remote server


FSClient themes.png


There are 3 main parts of the application. Calls, Current/Dialpad, and Accounts. There is also the options button in the lower right for configuration settings and optionally the Contact Search box under the dialpad if a contact plugin is loaded. The Calls and Accounts panes of the application can be hidden or shown by clicking the vertical button in the center with each of their respective names on it. Multiway calling is handled through the conference support. The application can be navigated using tab and arrow keys along with each pane having a short key to it.


The calls pane shows current active calls and the call history. Active calls are always shown at the top, with the call that is currently answered at the very top. You can jump to the first call in the calls list using the keyboard shortcut control+C. Hovering over a call will show the call details. Double clicking an active call will switch to that call. Double clicking an ended call will call that number back (on the same account it came in on). There is an arrow next to each call, a left arrow means outgoing call (away from softphone) a right arrow means incoming call (towards softphone). Calls also have an icon next to them to show call status. Call status colors are:

  • Grey - Ended
  • Black - Canceled
  • Red - Missed
  • Blue - Ringing
  • Green - Answered
  • Yellow - Hold

Right clicking on a call will show current actions, for live calls this includes things like Transfer, End Call, Add to Conference, Set your volume (local microphone boost), Set other party volume (boost their volume), it will also show any contact plugin actions.

Current / Dialpad

The current pane is in the center it shows the current call and any dtmf presses so far, the dialpad and any current actions that can be taken. The XFER button is to transfer, DND will reject any incoming calls, Speaker will switch the audio device from the main devices to the speakerphone devices (set in options). Yellow on a button means its enabled. You can dial using the mouse to click numbers or using a keyboard. To dial out on a specific account prefix the dial string with a '#' and the account number (for example #48001112222 will dial the number on account 4). You can jump to the number 1 key on the dialpad using the keyboard shortcut control+D. If the contact plugin supports it you can also have transfer aliases, right click on the XFER button to manage them when not in a call and right click on the button to use them while in a call.


Accounts pane shows your sip accounts, each account has a local name for reference and the current status of the account (normally accounts should show REGED). Click the Add button to add a new account. Once an account is added click the checkbox to enable it or disable it. Note that there is also the 'default account' if you only have one this will be it. The default account is what account is used to dial out by default. To jump to the first account in the list hit control + A. Right click on an account to check voicemail, edit it, force it to reconnect, delete it, or set it as the default account.

Contact Search Box

The contact search box will show up in the bottom center IF a contact plugin is used and it supports it. The default contact plugin is a simple name to number xml database. To access the contact search box click it or hit Control + f. Search box implementation is handled by the plugin itself, but in general type part of the name to search for the contact, up and down to scroll between results and enter to call (or right click for more options). Additional functionality are per plugin.

Conference Support (N-Way calling)

Any call can be moved into a conference at any time, simply right click on the call and select conference. This will shunt the call into the local conference. If there is not already a conference one is created. To see who is in the conference hover over the Conference button to the right of the Calls header in the upper left. To control the conference right click on the conference button. You can record the conference or control each user individually. Use controls include: setting a user as deaf makes it so they do not hear anyone, mute so no one else hears them, and a users energy level controls how loud they must be to be recognized as talking (higher the level the more background noise discarded). You can split a user out of the conference through the user controls too, returning them to a call with just you. If you leave the conference (ie to answer another call or by putting it on hold) it continues to run in the background, to rejoin simply double click the conference button.



  • .NET 4.0 (installer will install this if not found)
  • Windows XP SP3 or Later

To install FSClient use the installer found at: http://files.freeswitch.org/windows/installer/x86/FSClient.zip You can copy the installation folder to a USB drive for a portable version, just make sure .NET 4.0 is installed where you want to use it. Note config is not stored in the installation folder however if you copy your user.config into the app.config file it will read this locally and use this by default.


FSClient should be fairly screen reader and keyboard friendly. It does rely on UIA(User Interface Automation) support so any accessibility tools will need to support UIA. All controls should be labeled correctly. There are shortcut keys to move around between the 3 panes along with proper tab and arrow key support. Actions that require right clicking support shift + F10, single clicking is done through spacebar, and actions that require double clicking respond to the Enter key. If you find something not properly accessible feel free to let me know. Toggle buttons that use visual indicators will update their names to reflect their active state. Items that have a hover tooltip (Calls and the Conference only right now) you can force the tooltip to show by hitting control + H when keyboard focused on the item. The tooltip will go away if the keyboard focus changes, 20 seconds pass, or you hit Control + H again. Note most screen readers may not read tooltips, you can hit control + ? to show a popup message box with similar information. The incoming call bubble can be answered by clicking the answer button or hitting enter to accept the call.

Keyboard Shortcuts

  • Mute - Control + M
  • End Call - Control + E or Escape
  • Focus On Call List / Last Selected Call - Control + L
  • Focus on a specific call - Control + 1->9
  • Focus On Keypad Digit 1 - Control + D
  • Focus on Accounts - Control + A
  • Show Tooltip (Only on focused calls/conference) - Control + H
  • Show Messagebox with tooltip information - Control + ?
  • Focus on Contact Search Box - Control + F (If already focused Control + F again will select all)
  • Single Click - Space
  • Double Click - Enter
  • Right Click - Shift + F10

Compiling from Source

The source code for FSClient can be found in the freeswitch-contrib repo (git://git.freeswitch.org/freeswitch-contrib.git) under MitchCapper/FSClient. VS2010/VS2012 project files and a solution are provided. Ensure you have WPF Toolkit installed (just some libs the quick installer can be found at http://wpf.codeplex.com/ otherwise).

First get FreeSWITCH compiling properly on windows see Installation_for_Windows for details, the directory you compile it into does not matter and FSClient supports both x86 and x64 versions of FreeSWITCH. Make sure you use a copy of trunk for 2011-02-05 or later to have it work properly (at a minimum grab the latest mod_portaudio.c from after that date). You then can set the environmental variable FREESWITCH_SRC_LOCATION to the freeswitch build directory (Hint after compiling FREESWITCH_SRC_LOCATION\Win32 or FREESWITCH_SRC_LOCATION\x64 should exist). This can be set under Advanced on the System properties control panel or in VS.

There are 4 optional projects that are loaded by the solution by default but are not needed they can be unloaded to avoid building and any loading errors ignored, they are: JabraHeadset, Plantronics Headset, SimpleXMLContactPlugin, Setup. If FREESWITCH_SRC_LOCATION is set then when building the required files from the freeswitch build will automatically be copied into the FSClient working directory, there is also the link.pl script in the External Items that can be used to copy the files manually.

If you want to build the installer (Setup) you will also need the Windows Installer XML Toolset (http://wix.sourceforge.net/) or the setup project will not load properly.

If you are impatient and want to compile FSClient quickly without compiling Freeswitch first, simply install FSClient from the zip file, browse to C:\Program Files\FSClient folder and copy all the dlls, the conf folder, mod folder to your bin folder and build FSClient. Note: You risk not having the latest FS build, which might be a dependency in the current FSClient source.


Standard Options

  • Headset Device: This will always be set to None unless you have one of the headsets that there is a headset plugin for (Jabra and Plantronics by default). If you do have one of these headsets select it here and this will enable any advanced functionality your headset supports. NOTE: you do not need to have your headset show up here to use it, this just enables functionality like button presses, caller ID, etc. You can still use a headset not listed here like any other standard audio device.
  • Main Input / Main Output: These are the sound devices that are used by default during a phone call
  • Speakerphone Input / Speakerphone Output: These are the sound devices used when the speakerphone button is pressed
  • Ring Device - This is the sound device that an incoming call will ring on
  • Bring to Front on Incoming Calls - This will try and bring the FSClient window to the front when a call is incoming
  • Show Incoming Call Notification Balloons - Shows a systray like popup for each incoming call (shows caller ID and available actions)
  • Clear Key Presses In Call Stats on Disconnect - Will clear the DTMF history for all calls that are ended (rather than saving it by default)
  • Startup Layout - Choose which panels will be displayed or collapsed by default
  • Theme - Choose from the variety of themes for the dialer
  • Recording Path - Where call recordings should be stored (to record a call you must right click on it and click record)
  • Only Allow Numeric Input When Dialing - When enabled you can only dial numbers, # and *'s. This will automatically convert any letters typed to the proper key press per a normal keypad. If you want to be able to have dial strings with letters in them disable this feature.
  • Direct DIP: Dialing - Allows you to have FSClient directly connect to another SIP endpoint without going through a sip server. To do so use the sip: format for dialing (requires Only Allow Numeric Input to be off).
  • UPNP Nat Check - This enables FS to do its UPNP check on startup in most cases its not needed (costs 5-10 seconds extra startup time) is the equiv of -nonat to freeswitch
  • Check for Updates on Startup - Will hit a remote server and let you know if there is a new version of FSClient out
  • Reload Devices - Will do a hardware scan for any sound device changes (note cannot be used during a call), useful if things are plugged in or unplugged
  • Sofia Settings - Takes you to the sofia options.
  • Event Socket Settings - Takes you to the event socket options.
  • Plugin Settings - Takes you to the plugin options

Account Options

When creating or editing an account there are several options. Name / Account Number are FSClient only settings just for display purposes (or for the account shortcut number to use during dialing). To specify the port for an account in the server box put ip:port or host:port like:

Sofia Options

Configure various sofia settings, codec selection(right click on a codec to re-order it), nat config, tls options, and local bind ports. Values are the same as the normal freeswitch sofia config.

Event Socket Options

Allows you to set the ip, port, password, and optional ACL rule for the event socket.

Plugin Options

This will allow you to control which plugins are enabled or disabled and then configure any plugin options that they may have. Note that when you enable or disable a plugin you must restart FSClient for the change to take effect. You can have multiple headset plugins enabled at once, but only one contact plugin. Any plugins that are enabled but have an error occur will show a warning sign, hover over the warning sign to see the error.


  • Outlook Contact Plugin
  • Better configuration storage (option for in local folder for portable), maybe separate file for each configuration section
  • Freeswitch working dir not app folder (so no writing is required to local folder for proper vista/win7 apps)
  • Export call history on exit, and reload on startup
  • An option for a portable version (an option in the program to store the configuration in the working directory rather than User data dir, most likely checking for a local config before looking for the normal one is the easy way to solve this issue)
  • Remote Control plugin support (plugin able to make and accept calls, close FSClient, DND or Mute FSClient, also gets caller ID) would allow for external applications to better control FSClient or from a remote location
  • ZRTP support


Many plugin errors are caught and silently logged to the plugin.log file located in the app settings folder (generally c:\users\Username\AppData\Local\Mitch_Capper\*\plugins.log, see this file for any issues. You can also see the last error a plugin had by hovering over the warning icon on the plugin options page.

Contact Plugins


This is basically an internal contact book plugin. It is very simple allows you to associate a name with a number. The database is stored in the AppData folder for the application in an XML file. Right clicking on a call or contact will allow you to edit the alias. You can right click on a contact to call them (from the contact search box), double click to call them or hit return to call them.

Headset Plugins

Headset plugins enable advanced headset functionality. This generally includes opening/closing audio links, caller ID displays, button handling, touch screen interfacing, etc.


Note the Jabra PC Suite must be installed. The headsets are a bit ANAL and so try to be kind. Answering exactly as a call rings, muting instantly on a call, mashing on the buttons rapidly can cause the headsets to go into a state where events are not properly generated. Use them with a slight bit of TLC and they will work very well and without much thinking.

  • Button press support
  • Open/close audio link (make sure to set "PC Audio Control" to manual under the Jabra Control Center)
  • Caller ID Support
  • Touch screen support
  • Requires To Function: Download and install the Jabra PC Suite: http://www.jabra.com/Support/jabra-PC-suite (you do not need to have it run at startup however)



If you want to work on FSClient please do! You can work on the code base itself or plugins, if you would like to work with us please feel free to contact us on IRC we are generally in the main channel (Try for MitchCapper if he is there).

Plugin Development

There are two types of plugins, contact plugins and headset plugins. It is important to note that FSClient tries to catch and hide most errors plugins generate and send them to a log file. For writing plugins this can be annoying if you are not catching your own exceptions and so you may want to disable this code in FSClient. There are a few plugins included in the FSClient code base take a look at these for examples. Note since version 1.2 plugin file names MUST match the file naming convention or FSClient will not try to load them. Headset plugins must end in HeadsetPlugin.dll and contact plugins must end in ContactPlugin.dll. An example of a valid contact plugin filename is: SimpleXMLContactPlugin.dll.

Headset Plugins

All headset plugins must inherit from IHeadsetPlugin and each actual headset must be an instance of IHeadsetDevice. Your headset plugin should be able to handle if the user does not have the runtime/headset installed on the machine without throwing any errors, and certainly without popping up any message boxes. The headset manager will try to catch and hide any exceptions from the user, but these should not occur too often. There are some flags each headset device can specify, so the headset manager knows a bit about handling them. ANAL had the goal to only send plugins actual changes and avoid any duplicate events going to the headset (for example telling it to enable the audio link if already enabled), it is currently has no effect however and the headset manager tries to be anal with all. Aside from consuming events it is expected that headsets generate events for things like button pushes, etc if they support this.

Contact Plugins

Contact plugins can inherit either from IContactPlugin or the helper class SimpleContactPluginBase. SimpleContactPluginBase is the easiest to implement, and if you like the functionality of the built in SimpleXMLContactPlugin but just want a different datastore (either local or remote) it can be the way to go. SimpleContactPlugin has very low requirements, implement UpdateDatabase, SaveDatabase, LoadDatabase, and ProviderName and you are done. You want to store the database in number_to_alias_db which is a dictionary of string to string's of the phone number to the alias it goes with. There are additional functions you can implement to add additional functionality. IContactPlugin is a bit more complex to implement but gives more flexibility, The contact search box does next to nothing for you out of the box, so you must implement whatever functionality you want (if you want to support the contact find box). See SimpleContactBase for how it behaves and if you can emulate its functions to give a consistent user experience.

General Class/File Layout

Note plugins should only interact with utility classes (including generic editor/input box if desired) and broker. Plugins should generally avoid talking to other classes if possible.

  • Account - Handles account settings, generating the account config, and handle account changes.
  • Broker - This is the central manager class, for the most part other classes are generally meant to not talk to either other directly, but instead interact through the broker. This gives a consistant interface for activity. Broker is in charge of spinning up almost all other classes, initializing the freeswitch core, disperses events, and generates events for most common changes that occur.
  • Call - Handles call information, interpreting call events and call actions.
  • Conference - Tracks the conference for multi-party calling and people in the conference
  • Converters - GUI xaml converters for converting data to nice display formats
  • DelayedFunction - Allows for other classes to schedule tasks to occur in the future. Has one primary function, DelayedCall that takes a key, a function, and how many ms from now to cause it to happen. It checks for due functions every 200ms. If a key is past in then it will remove any other functions of the same key from the queue prior to adding the new one. This is useful for status changes to avoid firing stale changes.
  • EventSocket - Handles event socket preferences
  • Field - This class handles configuration data. It is how any dynamic configuration data should be stored. It makes it very easy to add or remove, settings, serialize them to XML and works with GenericEditor to give a GUI for them also. If you want to save more than a few settings (for example a bunch of settings for config generation) you want to use these.
  • FSEvent - Wrapper around the freeswitch core events providing some helper functions and general parameters.
  • GenericEditor - A multi-tab/categorized gui editor that works with the Field's classes to give an instant gui configuration for any Field settings with 0 gui coding.
  • IContactPlugin - Has the base class for any contact plugins(other than SimpleContactPluginBase) along with the Contact Plugin Manager that handles contact plugins.
  • IHeadsetPlugin - Has the base class for any headset plugins along with the Headset Plugin Manager that handles headset plugins.
  • IncomingCallNotification - Systray / balloon popup window for incoming calls
  • InputBox - Generic popup input box class for collecting input from a user
  • IPlugin - Base class for all plugins with abstract structure
  • MainWindow - The main window
  • Options - The main options GUI
  • PluginOptionsWindow - GUI for the plugin options
  • PluginManagerBase - This is a base class for any plugin manager. Handles some common tasks like loading plugins, saving/loading enabled plugins preferences.
  • PortAudio - The wrapper around all portaudio related items.
  • SimpleContactPluginBase - A base class that implements IContactPlugin partially to allow for simpler Contact Plugins
  • Sofia - Handles sofia settings, generating sofia config, and sofia changes
  • Utils - Basic FSClient utilities, debug logging, general paths, along with the BGAPI class. BGAPI executes freeswitch core API calls in the background in the order received. This is useful if you want to execute something but do not care about the result and do not want to tie the GUI up. Simply calling api_exec with the cmd and args is all it takes and it will return instantly.
  • Windows - Windows specific code, originally separated out when cross platform was a goal. Currently only manages the systray icon.
  • XmlUtils - XML helper functions