#protochat

smolboi is a prototype of a chat server written in Rust using async I/O, driven by the smol async runtime. It also contains a sample client, linetest, which is useful for testing & debugging.

#Building

1. Download the rust toolchain for your operating system.
2. Run cargo build in the root of this workspace to build all crates within the workspace simultaneously.
3. Run cargo run --bin server to start the server on localhost.
4. Run cargo run --bin linetest to start the client.

#Protocol

The codec for the chat protocol can be found in smolboi/src/protocol.rs in the protocol::packet module. In general the protocol works as follows:

The first two bytes on the wire(network byte-order) represent the length of the packet to be decoded. This tells a receiver how many bytes to read. The receiver should allocate a buffer of that size and pass the resultant buffer to Packet::decode(...).

NOTE: as a consequence a packet can be no greater than u16::MAX bytes long, e.g: 64KiB total.

It is important to note that this is not a general purpose serialization format, it is a purpose-built binary mapping of the packets enumerated by the protocol::packet::Packet type.

In general packet fields are arranged on the wire in the order they are listed in the enumeration, types will be encoded as follows:

• bool is encoded as a u8 which is either 0 or 1.

  • NOTE: any other integer value represents a decode error and must be rejected.

• String is encoded as a length (u16) and then a series of bytes representing a UTF-8 encoded string.

  • NOTE: any other encoding must be rejected by a conforming receiver.
  • NOTE: attempt to encode a string of length greater than u16::MAX is an error and must be rejected by a conforming sender.

• Integer types will be represented on the wire as bytes in network endian order.

• Arrays will be encoded similarly to strings: however the u16 length prefix will represent the number of elements in the array. All arrays will be heterogeneous: and contain only the objects described above.

#Terminal Library

The linetest crate contains basic line editing functionality, as well as a scrollable line-oriented buffer. This client is cross-platform, w/ the low-level terminal handling provided by the crossterm crate. Current functionality includes:

• Line navigation (Home/End, PgUp/PgDown, etc.)
• Ability to move the cursor (Left, Right)
• Ability to insert text in the middle of a line
• Responsive to terminal resize events
• The span always remains centered around the cursor, even in the face of resize events/cursor mainpulation.