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meshenger

Meshenger is a Forban-inspired messaging software used for a speculative broadcast communication project. The starting point is an electronic messaging system running on a wireless mesh network. The messages propagate through the network when devices that come in contact with each other synchronize their content. It is non-hierarchical, every node receives, relays and broadcasts messages.

Using Meshenger. Devices detect each other by continously broadcasting an identifier packet while listening to those of other nodes. As soon as two (or more) nodes detect each other they will try to synchronize the messages on each node.

The users of the network can interface with the nodes to send or receive messages by using the webbrowser of their smartphone or computer. The messages can be received and sent at any time, but they are only synchronized in the network when other nodes are encountered.

Meshenger is supposed to run on an Open-WRT router that has been configured to work in mesh networks (for a configuration how-to see below).

Configuring a router for Open-WRT and Meshenger

Flashing and preparing

Meshenger requires routers that both support Open-WRT and have at least one USB port (List of Open-WRT routers here). We have used the following models: TP-Link MR-3020, TP-Link TP-WR703n and TP-WR842nd.

Open-WRT have a guide for each supported device that tells how to best flash your specific device with Open-WRT. (Article on flashing)

After flashing proceed through the first login as described (here)

You are going to need to have an internet connection to your router, the easiest thing is to hook it up to the router.

Alternatively if you use OSX you can enable internet sharing (make sure to set your OSX machine as the gateway and DNS server for your router in /etc/config/network)

System configuration

To use your router for Meshenger you're going to need to run the whole filesystem from a USB-Drive.

Make sure that said USB-Drive is formatted as such:

- one ext4 partition

- one linux-swap partition (32mb seems to be sufficient so far)

Next enable USB-Storage on the router:

$ opkg update

$ opkg install 'block-mount kmod-usb-storage kmod-usb2 kmod-fs-ext4

To check if it works try $ ls /dev/. You shoud see sda, sda1 and sda2

Now mount the USB-Drive:

$ mkdir /mnt/sda1

$ mount -t ext4 /dev/sda1 /mnt/sda1

Copy the whole filesystem to the USB-Drive:

$ mkdir -p /tmp/cproot

$ mount --bind / /tmp/cproot

$ tar -C /tmp/cproot -cvf - . | tar -C /mnt/sda1 -xf

$ umount /tmp/cproot

Edit fstab

$ vi /etc/config/fstab

Make config mount look like:

config mount 
    option target /
    option device /dev/sda1
    option fstype ext4
    option options rw,sync
    option enabled 1
    option enabled_fsck 0

Reboot the device ($ reboot -f) and use $ df -h to confirm device now runs off the USB-Drive

Next we configure the swap partition

$ mkswap /dev/sda2

$ swapon /dev/sda2

Edit fstab again now make the swap look like this:

config mount
	option device   /dev/sda2
	option enabled

Wireless configuration

The next section is on how to set up the network interfaces to work with B.A.T.M.A.N the mesh networking protocol. It is more or less a summary of what's written (here)

$ vi etc/config/wireless and edit the wireless interface to look like this:

Dont forget to remove the line that disables wireless

config wifi-iface 'wmesh'

	option device  'radio0'

	option ifname  'adhoc0'

	option network 'mesh'  

	option mode		'adhoc'

	option ssid     'mesh'          

	option bssid '66:66:66:66:66:66'

Next up is $ vi etc/config/wireless where we add this interface:

config interface 'mesh'

	option ifname 'adhoc0'

	option mtu '1528'

	option proto 'none'

Lastly we edit $ /etc/config/batman-adv to tell it which interface to use.

config mesh 'bat0'

	option interfaces 'adhoc0'

	option 'aggregated_ogms'

	option 'ap_isolation' 

	option [..]

$ /etc/init.d/network restart to make the changes take effect.

If you have set this up properly on more than one node, the nodes should be able to see each other. Test with $ batctl -o

Make sure that you have the same version of batctl and openwrt on all nodes you plan to use. $ uname -a && batctl -v to see the version information.