.. _starting_the_ecflow_server:

Starting the ecFlow Server
//////////////////////////

The executable ecflow_server is used to start an ecflow_server using the
default port number or that defined by the environment variable
ECF_PORT.

.. code-block:: shell

    cd ECF_dir1
    nohup ecflow_server & # start ecFlow with **default** port 3141    

Multiple ECFs can be run on the same host using different port numbers.
There are two mechanisms for specifying the port number:

-  Using arguments on the command line. i.e. ecflow_server --port=3141

-  Using the Environment variable. ECF_PORT

If both are specified the command line argument takes precedence

.. code-block:: shell

   cd ../ECF_dir2
   ecflow_server –-port=3142& # start ecFlow with port number 3142
   cd ../ECF_dir3
   export ECF_PORT=3143
   ecflow_server &            # starts ecFlow with port number 3143

**Note:** the ECFs are started in different directories so that the
output and checkpoint files are not overwritten

.. rubric:: ecflow_ui configuration

Adding a new server to ecflow_ui adds the definition to the file::

  ~/.ecflowrc/servers. 

This can be modified directly.

.. rubric:: Start-up scripts

A start-up script, :code:`ecflow_start.sh`, is a useful way of starting and configuring ecFlow server.
An example start-up script is included in the default installation of ecFlow. A start-up script can be used to:

- configure some of the default ecFlow variables
- check that an ecFlow server is not already running (by using :code:`ecflow_client --ping`)
- set the appropriate environment (or do it in .profile or .cshrc)
- backup previous log files and checkpoint files
- and, eventually, launch :code:`ecflow_server` in the background, and alert operators if a problem occurs while starting the server.

Two ecFlow servers cannot be started on the same host machine with the same port number.
To allow users that want to run multiple ecFlow servers on the same host machine, the script
:code:`ecflow_start.sh` can choose a difference port number based on the unique user ID.

Which ports are being used can be checked with netstat. To list
all open network ports on your machine, consider running the following command:

.. code-block:: shell

   netstat -lnptu
  
Here is a breakdown of the parameters:

-  l - List all listening ports

-  n - Display the numeric IP addresses (i.e., don't do reverse DNS
   lookups

-  p - List the process name that is attached to that port

-  t - List all TCP connections

-  u - List all UDP connections

When using non-default ecFlow servers, ecflow_ui needs to be configured
to recognise the port used. This can be done in the Manage servers dialog.

.. figure:: /_static/ug/starting_the_ecflow_server/image1.png
   :width: 4.02282in
   :height: 2.60417in

   Viewing new ECFLOW servers with ecflow_ui