Frequently Asked Questions

This page lists common questions about Saros and known issues. If your question is not answered here you should look around the Contact area. There you will find more information that may help you.


A Saros cycle is an eclipse cycle, i.e. after one Saros cycle the Sun, Earth, and Moon return to approximately the same relative geometry. When creating the plug-in, Riad Djemili thought this would make a nice name for an Eclipse plug-in about Pair Programming, where driver and observer cycle their roles while revolving around code of interest.

No, Saros is not language-dependent as it works on a character-level.

These tables compare known alternatives to Saros.

In the following we are using these definitions:

  • Open-Source - A software using a license contained in the list of approved licenses of the Open Source Initiative
  • Commercial - It is not possible to use the software for free without limitations.
  • Freeware - You can use the software for free, but the code is not published.
  • Self-hosted - The possibility to host a corresponding server that manages the connection or also the shared workspaces.

Web-Based IDEs

Name Category Self-hosted
CodeEnvy Commercial No
Cloud9 Commercial No


Name IDE Category Self-hosted
FlooBits Atom, Emacs, IntelliJ IDEA, Neovim, Sublime Text Commercial Yes
Saros Eclipse, IntelliJ IDEA (and IDEs based on the IntelliJ platform) Open-Source Yes
Live Share Visual Studio (Code) Freeware No
Teletype Atom Open-Source Yes

Stand-Alone Editors

Name OS Category Self-hosted
Gobby Win, Linux, Mac OS Open-Source Yes
SubEthaEdit Mac OS Open-Source Yes


  • Saros requires much less bandwidth (as it transfers only editing commands, not screen contents)
  • Each Saros participant can use a different screen resolution, different IDE-settings, keyboard layout – and even different IDEs.
  • Saros does not slavishly chain users together. For instance, Saros allows multiple participants to write to the same file in different spots at the same time. It also allows one participant to look something up (in the same or a different file) while another user is writing.
  • Saros scales to more than two participants naturally.


  • Saros does not support sharing information which occur outside of the IDE (so even all participants can run the application under development independently, they cannot see the others doing so).
  • Saros requires each participant to have an Eclipse installation setup.

Saros supports up to 5 users (see here for the current restrictions in Saros/I). However, this is not a hard limit. But the sixth and seventh and n-th user will get the same gray-ish color.

In theory, the same version of Saros will run on any platform for which there is a version of Eclipse/IntelliJ. We generally perform our testing on multiple flavours of Windows, Linux and Mac OS X.

SVN: Yes, you can. In theory, there should be no problems since so called derived files are not shared by Saros. Usually, the corresponding Eclipse plugins (such as Subclipse) take care of setting the “derived” attribute for “.svn” directories (as well as Java “.class” files, which are also not synced). If in doubt or if you don’t use such plugins, you can always set this attribute on your own: Just right-click on the respective directory, select “Properties”, and check the attribute “Derived”.

Git: To make completely sure that Saros won’t mess with your versioning data, you might consider a folder layout where your Eclipse project(s) reside on a level below the .git folder (see below). That’s the way we organize our own source code (even though we do so for other reasons). We’re working on Saros’s Git-friendliness so it also supports repositories adhering to the one-project-per-repository policy.

Safe layout (“multiple projects per repository”)

├── .git
├── module-a  <-- totally safe to share
│   ├── src
│   ├── test
└── module-b  <-- so is this one
    ├── src
    └── test

Risky Layout (“one project per repository””)

my-project  <-- you shouldn't share this one
├── .git
├── src
├── test
└── readme.html

You can find the Saros related logs in your eclipse workspace. The current workspace directory is shown if you open "Switch Workspace" > "Other...".

  • IDE logs - <workspace>/.metadata/.log
  • Saros logs - <workspace>/.metadata/.plugins/saros.eclipse/log/<date>/*.log

This is an alpha. See here for restrictions.

The log files for IntelliJ platform based IDEs are located in the IDE system directory (here called IDE_SYSTEM_DIR). An overview over all configurations is given on the support forum. For specific releases, see the information for 2019.3 and earlier or 2020.1 and later.

The Saros log files are located in [IDE_SYSTEM_DIR]/log/SarosLogs/*.log.

If you are encountering IDE errors connected to Saros (which will be displayed by a red, blinking symbol in the bottom right corner of the project view; the error can be viewed in more detail by clicking the symbol), please also include the IDE logs. They are located in [IDE_SYSTEM_DIR]/log/ and are named idea.log (the log will be truncated at some point and older logs will be moved to idea.log.1, etc.). Please have a look at the contained timestamps to provide the correct file.

Before attaching any log files, please make sure to redact any private information that you do not wish to make publicly available.

Network Issues

The real bandwidth problem is usually not during a Saros session, but rather with the project synchronization needed for starting one, which may take quite long (many minutes) for larger projects over a low-bandwidth connection. Make sure all participants have local copies of the project that are not too different before the session starts.

Home users (using DSL) and most corporate networks employ NAT. Computers behind a NAT can open TCP connections to other computers, but other computers cannot open TCP connections to them.

So how can two Saros users that both sit behind a NAT create a joint Saros session?

  • Saros uses an XMPP server to get in contact with the other participant(s). Companies can run their own XMPP server for maximum privacy; home users can use almost any public XMPP server.
  • Throughout the session (if possible) Saros uses Socks5 connections (direct or mediated) between the participants. Saros supports optional UPnP port forwarding to improve chances of direct connections. (see Saros network preferences)

Troubleshooting Socks5 Bytestream Establishment

If you keep getting Mediated Socks5 Bytestreams or In-Band Bytestreams, other peers cannot connect to you directly (cannot create a TCP connection to you). What can you do to improve chances?

  • Your default Socks5 proxy port (7777) might be in conflict. You can change the Socks5 proxy port in the Saros network preferences.
  • Your firewall might block connection requests for/from Saros. You can configure your firewall to allow Saros (Eclipse, Java) communication.
  • If you are connected through a Universal Plug and Play compatible gateway device, you can enable Saros to perform a port mapping for the computer it is running on and make it reachable from the outside. The UPnP option can be enabled in Saros network preferences. If your gateway device is not found, it might require enabling UPnP support as well.
  • If your gateway is not UPnP compatible, it may be possible to manually configure a port mapping for the Socks5 proxy port and your private IP to be reachable from the outside. Consult your gateway (e.g. Router) manual for port mapping or sometimes labelled virtual servers.

What Might Stop You From Using Socks5

Some factors might prevent you from using S5B. Lets have a quick look at the S5B protocol when you want connect a buddy.

  • Your Saros requests your connected XMPP server for an available proxy.
  • Your Saros detects its local and global network addresses.
  • Your Saros sends the list of your addresses and the proxy address (if any) to your buddy’s Saros.
  • Your buddy’s Saros attempts to create a TCP connection to any of the addresses you provided.
    • If your buddy connected to one of your addresses, you’ll get a direct S5B connection.
    • If your buddy couldn’t connect to your addresses but to a proxy and so does your Saros, you will get a mediated S5B connection.
    • Otherwise the S5B connection fails.

Saros actually attempts the S5B creation in both directions, so both sides attempts to connect each other. This improves chances of one peer connect to the other one. You can check your contact list to see which bytestream type is established between you and a contact (if any).

For further information check out data connections in Saros on our network layer page. Important: The page may be quite outdated as it is part of our legacy documentation and has not been migrated to our new documentation. It can be found here.

We think it is basically a problem with Eclipse, which keeps checking for updates to all plug-ins that you have installed. To work around this problem, uncheck “Contact all update sites during install to find required software” in Eclipse’s installation dialog.

Go to Eclipse -> Saros -> Preferences -> General -> Network Connections and make sure, that there are no proxy settings checked.

Yes. See the Installation and setup page for information on setting up your own local XMPP server.

All edits go through a server. Because it can be used with a public server, Saros attempts to be courteous and sends edits out in intervals (a few hundred milliseconds), so the server is not overloaded. However, everyone in your session can reduce this interval in order to remove the perceived latency. Just go the Saros advanced preferences and enter a lower value in the box labelled “Interval (in milliseconds) between outgoing edits to peers”.

Known Issues

The following issues are general issues that arise from the general approach of Saros.

If you are searching for bugs look into our issue tracker.

  • Transferring large amounts of data during session initiation (project synchronization) can take a lot of time. Do as much of the synchronization via your version control repository as you can to keep session initiation fast by using “copy of existing project” when accepting a session invitation.

  • Refactoring operations can produce a huge number of events to be transferred by Saros, which may take very long and can thus be confusing for participants.

  • In particular, on-the-fly refactorings such as ‘rename’ perform one such (possibly large) set of operations for each keypress. It is wise to avoid these operations.

  • Be aware that Saros transfers only the text editor pane. When you use other elements of Eclipse, e.g. structure browsers or the HTML browser, your session mates cannot automatically see this. Thus, talking aloud about the things that you are doing there is probably required to make them aware of your actions.
  • You and your session mates should use the same editor settings regarding formatting and encoding; in particular regarding TAB width, TAB/spaces handling and character encoding.
  • If you are sharing a project which is managed by a source code management system such as Subversion, make sure that all participants have compatible versions of the SCM plugins installed. Otherwise Saros might corrupt the version information or transfer revision data unnecessarily.