Introduction / FirstSpirit Server configuration / Configuration files (FirstSpirit Server) / Java VM and Wrapper (fs-wrapper*.conf) / IPv6 support

IPv6 support

Table of contents

FirstSpirit supports simultaneous communication via IPv4 and IPv6 (“dual stack”). -D parameters can be used to configure whether the client/server should run primarily under IPv4 or IPv6 or only under one of the two versions. These parameters are specified if required for the server into the file fs-wrapper.conf, for the client in the connection settings (see Configuring connection settings and page Start page).

Using the configuration

IPv6 use can be completely deactivated, i.e. all communication takes place via IPv4 for both the server and the client. This is the default configuration.

The current IPv configuration for the client or server is recorded in the log file fs-server.log at the start, e.g.

INFO  08.03.2013 09:09:35.381 
( IPv4 preferred

Additional modes:

  • IPv4 disabled
  • IPv6 disabled
  • IPv6 preferred

Server configuration

If the configuration file fs-server.conf specifies the parameter SOCKET_HOST (see Configuration parameters), the server connects with all addresses found by the DNS query (IPv4 and/or IPv6).

With the configuration


the server only connects with the IPv6 address, even if there is an IPv4 DNS entry. The parameter is only evaluated if the parameter SOCKET_HOST is specified in the file fs-server.conf. This parameter is deactivated by default (false).

If the configuration file fs-server.conf does not specify the parameter SOCKET_HOST, the server listens to all addresses, regardless of whether they are IPv4 or IPv6. Exception: IPv6 is deactivated by the parameter

Client configuration

The following -D parameters can be used for client configuration:

The client only connects via IPv4.


The client only connects via IPv6.


If the server can be reached via IPv4 and IPv6, the client tries to connect via IPv6 first. By default, the client will try to connect via IPv4 first.


These parameters are deactivated by default (false).

If the server can be reached via IPv4 and IPv6 but only one connection is working, this connection is used automatically regardless of the setting configured via the -D parameters.

In order to specify a numerical IPv6 address in the connection settings of the client (e.g. via the FirstSpirit start page or the WebStart configuration in ServerManager), the address must be written in square brackets, e.g.


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