Upload sketch remotely through a serial-IP-serial connection
I've been searching through the net for some days, in order to discover how I could easily upload a sketch to an Arduino that is not phisically connected to my PC, but instead that is connected to an another one, that belongs to the same LAN. I mean:

PC1-SERVER
Arduino Uno is connected to this PC with classic USB cable.
This PC is running Ubuntu linux, and sees Arduino as a serial port /dev/ttyACM0.

PC2-CLIENT
This is the PC where I create and compile the sketch. 
I want to upload the sketch to the Arduino Uno described above (so, connected to SERVER, port /dev/ttyACM0)

SOLUTION:
server-side commands:

Code:

sudo apt-get install ssh-server ser2net

sudo passwd root    (to set the root password)

sudo reboot


client-side commands (assuming 192.168.0.7 as IP address of SERVER):

Code:

ssh -L 8086:localhost:8086 root@192.168.0.7 \
'/usr/sbin/ser2net -d -C "8086:raw:600:/dev/ttyACM0:115200 NONE 1STOPBIT \
8DATABITS -XONXOFF LOCAL -RTSCTS HANGUP_WHEN_DONE "'


you can then upload sketches to arduino doing this:

Code:

avrdude -C /path/to/avrdude.conf -p atmega328p -c arduino -P net:localhost:8086 -U flash:w:/path/to/file.hex:i


NOTE:
In Eclipse, if you are using the arduino plugin, just place "net:localhost:8086" in the configuration panel, where "port:" field is required.

This solution was also posted on arduino forum.