SMP (SimpleX Messaging Protocol) server setup

Short guide on how to install SMP server to be used with SimpleX Chat.
SimpleX Chat

This guide has some notes and additions for people who are less experienced with Linux.

If you are setting up a new host machine, I suggest using Ubuntu Server 22.04 LTS. Not only it is well-supported and reliable, but also, SimpleX Chat author (epoberezkin) provides SMP server executable binaries for Ubuntu Server 20.04 LTS and newer (to save you the hassle of having to build them yourself).

Host machine (Ubuntu Server) setup

Open Ports

SimpleX Chat uses port 5223 to communicate with the SMP server. Make sure this port is open and the host machine is reachable on this port from the Internet.

Preparation

Update your host's system:

sudo apt update
sudo apt upgrade
sudo reboot

Install micro text editor: (it has familiar Windows-y shortcuts, Ctrl+X/C/V for clipboard, Ctrl+Q to quit, if you prefer any other editor, please ignore this step)

sudo apt install micro

Download and install the SMP server

Download the SMP server binary:

wget https://github.com/simplex-chat/simplexmq/releases/download/v3.0.1/smp-server-ubuntu-20_04-x86-64

Move the binary to the appropriate directory: (/usr/local/bin is for executables NOT managed by package managers)

mv smp-server-ubuntu-20_04-x86-64 /usr/local/bin/smp-server

Make the binary executable:

chmod +x /usr/local/bin/smp-server

Check that the executable binary is properly installed:

which smp-server

should return:

/usr/local/bin/smp-server

Initialize the SMP server

If you have a fully-qualified domain name: (for example, smp.mysite.net)

smp-server init -l -n smp.mysite.net

If you are using just the IP: (for example, 199.199.199.199)
If you are running behind NAT, use the external IP address.

smp-server init -l --ip 199.199.199.199

IMPORTANT: After the SMP server initializes, it will give you a Fingerprint. Copy and save it. (Ctrl+Shift+C to copy from terminal)

Setup guide suggests copying the private CA key (/etc/opt/simplex/ca.key) to another machine and then deleting it from the host machine. I haven't done this.

Create a systemd service

To automate starting the SMP server, create a systemd service:

micro /etc/systemd/system/smp-server.service

Then write the service's definition:

[Unit]
Description=SimpleX Messaging Protocol Server
After=network.target

[Service]
Type=simple
ExecStart=smp-server start
Restart=always
RestartSec=3
KillSignal=SIGINT

[Install]
WantedBy=multi-user.target

(Ctrl+S to save, Ctrl+Q to quit)

Since you just added a new service, refresh the system daemon:

sudo systemctl daemon-reload

Enable the new service so it starts when the server is started:

sudo systemctl enable smp-server

Start the new service:

sudo systemctl start smp-server

Check the status of the running service:

sudo systemctl status smp-server

SMP server address

Now, using the fingerprint and domain name (or IP address) from above, create the full SMP server address. It should look something like:

smp://u2dS9sG8nMNURyZwqASV4yROM28Er0luVTx5X1CsMrU=@smp4.simplex.im

smp://hpq7_4gGJiilmz5Rf-CswuU5kZGkm_zOIooSw6yALRg=@45.33.61.248

IMPORTANT: Copy and save this value. (I will refer to it as the "SMP Server Address")

Testing

Do this on your own machine. Or if you don't have a Linux machine, you can do it on the host machine too I guess?

Install the SimpleX Chat terminal client (command from the SimpleX Chat site)

curl -o- https://raw.githubusercontent.com/simplex-chat/simplex-chat/master/install.sh | bash

If you don't trust running scripts from the web (and you should not!), download a pre-compiled binary or install SimpleX Chat via official instructions.
Pre-compiled binaries for SimpleX Chat terminal client
SimpleX Chat terminal client installation instructions

Run SimpleX Chat and tell it to use your new SMP Server Address: (using the parameter tells the client to use the server only for this session - see below for permanent change)

simplex-chat -s smp://xxxxxxxx@xxx.xxxxxx.xxx

simplex-chat -s smp://xxxxxxxx@nnn.nnn.nnn.nnn

Answer the initial questions such as your display name.

Now you are in the Simplex Chat terminal client. Type /help for list of commands.

Create a connection:

/connect

If you get an error:

smp agent error: BROKER {brokerErr = NETWORK}

It means your SMP server is not running or is not reachable. Check the connection between your client machine and your host machine. Check that port 5223 is open on the host machine. Log back into the host machine and start / restart the SMP server service (see above).

If everything is OK, you should get a very long invitation link. Copy it from the terminal (Ctrl+Shift+C) and send it to the second client (SimpleX Chat on your phone, for example). Open the link on the second client, which will start the conversation.
If you are able to communicate between the two clients, you're all set!

Using the new SMP server

Now you can use your new SMP Server Address in all of your clients.
For terminal client:

/smp_servers smp://xxxxxxxx@xxx.xxxxxx.xxx

/smp_servers smp://xxxxxxxx@nnn.nnn.nnn.nnn

For mobile clients, open Settings, find an option "SMP servers", toggle "Configure SMP Servers" to on, then enter the SMP Servers Address for all servers you want the client to use.

IMPORTANT: To use the new SMP server, re-establish connections to your contacts once you change SMP server(s) in your client.