Tested on Linux, macOS, Windows (via MSYS2 and WSL), OpenIndiana, FreeBSD, OpenBSD, DragonflyBSD, NetBSD. Clear Linux?

Roadmap

• Start by local connections, 1 client to 1 server
• 1 client to 1 server, local to remote connections (backup lab7)
• many clients to 1 server, server one thread per client
• ...
• Leave clipboard server replication for later (single mode first)

TODO

• on app copy, its write() does not wait for the servers read() of course. However, the server may fail to allocate enough memory to receive the data, in which case nothing, in practice, was copied to the server's region. So the app should wait for a reply from the server saying it failed, and clipboard_copy should return 0.

Apps (clients)

• Apps may connect to more than one local clipboard server, by the server's UDS, whose path is passed to clipboard_connect.
• Apps identify a clipboard by int clipboard_id, returned by clipboard_connect.
• Each connection to a clipboard is handled by the library.
• Clients may be multithreaded for the 20, which means the libary has to be thread-safe on _copy requests to the same region. (serialize)

API Library (interface)

• Write void *buf from app to server socket (clipboard_copy).
• Read into the app's void *buf from server socket (clipboard_paste).
• These two write/read follow a protocol between the library and the local clipboard server.
• Connect to the local clipboard server by UDS (or shared memory (unrelated processes) if void *buf too big - Performance optimization the prof. suggested).
• SOCK_STREAM
• copy/paste: do only one write (two recvs) to minimize critical region, this forces the use of a msg buffer instead of a struct

Clipboard (server)

• When starting, connect to another clipboard server given in the argv[].
• Synchronize our local regions with the other remote servers.
• Each local clipboard should have one thread that receives connections from local applications.
• Each local clipboard should have one thread that receives connections from cooperative remote clipboards.
• Each local clipboard should create one thread for every connected application.
• Regions will be protected by a lock.

Local protocol

• Between library and clipboard server
• Message is:
• command is 1 byte uint8_t
• region is 1 byte uint8_t
• size is 4 bytes uint32_t
• data is whatever size