A few notes about interfaces manipulations, general networking, etc.
Interfaces manipulations
Setting up a bridge
Assume you have two interfaces eth0 and eth1 and you want to put them on the same link.
# With ip link
ip link add name br0 type bridge
ip link set br0 up
ip link set eth0 up
ip link set eth0 master br0
ip link set eth1 up
ip link set eth1 master br0
ip link set eth1 nomaster
ip link set eth1 down
ip link set eth0 nomaster
ip link set eth0 down
ip link delete br0 type bridge
# With brctl from bridge-utils
brctl addbr br0
brctl addif br0 eth0
brctl addif br0 eth1
ip link set br0 up
ip link set br0 down
brctl delbr br0
Simple servers and clients
Using socat
Echo server listening on one port and answering exactly what it receives.
The fork instruction allows it to fork and accept multiple connections.
socat TCP4-LISTEN:$PORT,fork EXEC:'/bin/cat'
Network file systems
SSH filesystem
How to locally mount a remote folder.
sshfs -o IdentityFile=$ID $SSH_DIR -o volname=$VOLUME -o auto_cache,reconnect,defer_permissions,noappledouble,nolocalcaches,no_readahead $MOUNT_DIR -o exec