Server for online board for working with clients. In current version communication between them is carried out using JSON format. Message is consists of three parts:
- Size of header in 8 bytes as uint64_t
- Header in JSON format:
{
int: client_id,
string: method,
int: argument_size,
}
- Arguments in JSON format, the number and type of which depends on the method.
- s_add_layer
{
int layer_id,
double[2]: position,
double: scale,
string: layer_type,
object: layer_data
}
- s_clear_board
No arguments - s_delete_layer
{
int: layer_id
}
- s_undo
No arguments
- c_init_client
{
int: client_id,
}
- c_finish_board_init
No arguments - c_add_layer
{
int layer_id,
double[2]: position,
double: scale,
string: layer_type,
object: layer_data
}
- c_confirm_add_layer
{
int: layer_id
}
- c_clear_board
No arguments - c_delete_layer
{
int: layer_id
}
When new client is connected, server calls c_init_client() to give new cliet it's id and confirm successful connection. After that each layer on board must be added on client's canvas. At the end of inicialization client notified about completing all init operations with call c_finish_board_init().
When client creates new layer it calls s_add_layer() following which server calls c_add_layer() for all other clients except layer's creator and confirms successful adding with calling c_confirm_add_layer() for creator. Confirm is necessary to give layer's creator new layer's unique id, that could be generated just on server.
When client deletes one of layers it calls s_delete_layer() with layer's id following which server calls c_delete_layer() for all other clients except layer's deleter.
When client calls s_undo() to cancel it's last action server defines the type of last operation made by this client and calls corresponding methods for all clients (including caller). For example if last operation was adding layer then for all clients would be called c_delete_layer().
When client calls s_clear_board(), server clears it's canvas and calls the similar method c_clear_board() for all other clients except caller.