I have 2 Raspberry Pis in my system. One can be 'docked' to the other one and some time later it can become 'undocked'. While docked, the 2 Pis will have a connection between 2 GPIO pins ( 1 pin on each Pi ). So there will be 1 wire that connects both Pis. These 2 Pis will be the only systems on the 'bus', it is only a point to point connection.
I am aware of the Dallas 1-wire protocol ( have used it with a temp sensor on the Pi but it had a kernel driver that did all of the work ), but I know it is difficult to meet timing and there is no easy way to use it from Userspace. I have heard of making a UART at 115200 Baud emulate the protocol but I have no free UARTs in my system. So Dallas 1-wire is not feasible.
Basically, when the 2 Pi's are docked, the master will send the slave an SSID string and there will be a simple ping-like operation ( ping from slave / ACK from slave ) that will notify both Pis they are docked. So the communication is very simple.
This can be completely proprietary with emphasis on simplicity. I can use Python or C or Qt ( C++ ), or just Bash if possible...
I would greatly appreciate any help or guidance on how to achieve this. What is the best, very simple way to implement this communication?