Low-level protocol tests.

Cargo.lock

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Cargo.toml

 async-tungstenite = { version = "0.3", features = ["tokio-runtime"] }
 env_logger = "0.7"
 log = "0.4"
+rmp-serde = "0.14"
 fswatcher = { git = "https://github.com/mgottschlag/fswatcher-rs.git" }

src/bin/protocol-tests.rs

+extern crate rmp_serde as rmps;
+extern crate serde;
+
+use rmps::Serializer;
+use serde::Serialize;
+use twfss::protocol;
+
+fn print_serialized_deserialized(packet: protocol::Packet) {
+    let mut buf = Vec::new();
+    packet
+        .serialize(
+            &mut Serializer::new(&mut buf)
+                .with_struct_map()
+                .with_string_variants(),
+        )
+        .unwrap();
+    println!("Serialized: {:?}", buf);
+    let packet: protocol::Packet = rmps::decode::from_slice(&buf).unwrap();
+    println!("Deserialized: {:?}\n", packet);
+}
+
+fn main() {
+    // Open questions:
+    // - Do we actually need the "response" field? Actually, separating the ID range so that
+    //   server->client events get IDs from the range between 2^31 and above would be enough.
+
+    // The low-level protocol needs to implement two basic pieces of functionality: It needs to be
+    // able to implement remote procedure calls from the client to the server, and it needs to
+    // provide a method for the server to send asynchronous events. A protocol for both cases is
+    // outlined below, where each packet is sent as one WebSocket message.
+    //
+    // Remote procedure call:
+    // - The client allocates an ID from the range between 0..2^31-1 that is not currently in use
+    //   for another RPC in progress.
+    // - The client prepares a packet with this ID, "response = false", and the appropriate
+    //   payload and sends the packet to the server.
+    // - The server receives the packet, processes the request and sends a packet back with the
+    //   identical ID and "response = true".
+    // - In case of an error, the payload has the type "Error" which in turn contains the error
+    //   type.
+    // - Unpon reception of the response, the client is free to reuse the ID for further RPCs.
+    // Note that this protocol does not allow the client to cancel an RPC that is currently in
+    // progress - implementing such functionality is difficult, error-prone, and most likely not
+    // worth the effort.
+    //
+    // Server-side event:
+    // - The server creates a packet with the ID 2^31 and the event content and sends it to the
+    //   client.
+    // Note that the client does not have any method to acknowledge event reception. As events are
+    // asynchronous compared to RPCs on the same connection, the event type needs to be designed in
+    // a way that no such temporal information is necessary to process the events.
+    // TODO: Example to demonstrate the problem.
+
+    println!("Without request content:");
+    let packet = protocol::Packet {
+        id: 42,
+        response: false,
+        payload: protocol::PacketPayload::ServerInfo,
+    };
+    print_serialized_deserialized(packet);
+    // Should be: [131, 162, 105, 100, 42, 168, 114, 101, 115, 112, 111, 110, 115, 101, 194, 167, 112, 97, 121, 108, 111, 97, 100, 129, 170, 83, 101, 114, 118, 101, 114, 73, 110, 102, 111, 192]
+
+    println!("\nWith request content:");
+    let packet = protocol::Packet {
+        id: 42,
+        response: true,
+        payload: protocol::PacketPayload::ServerInfoResponse(protocol::ServerInfoResponse {
+            version: "0.1".to_owned(),
+        }),
+    };
+    print_serialized_deserialized(packet);
+    // Should be: [131, 162, 105, 100, 42, 168, 114, 101, 115, 112, 111, 110, 115, 101, 194, 167, 112, 97, 121, 108, 111, 97, 100, 129, 178, 83, 101, 114, 118, 101, 114, 73, 110, 102, 111, 82, 101, 115, 112, 111, 110, 115, 101, 129, 167, 118, 101, 114, 115, 105, 111, 110, 163, 48, 46, 49]
+
+    println!("Error:");
+    let packet = protocol::Packet {
+        id: 42,
+        response: true,
+        payload: protocol::PacketPayload::Error(protocol::Error::InvalidParameter),
+    };
+    print_serialized_deserialized(packet);
+    // Should be: [131, 162, 105, 100, 42, 168, 114, 101, 115, 112, 111, 110, 115, 101, 195, 167, 112, 97, 121, 108, 111, 97, 100, 129, 165, 69, 114, 114, 111, 114, 129, 176, 73, 110, 118, 97, 108, 105, 100, 80, 97, 114, 97, 109, 101, 116, 101, 114, 192]
+}

src/lib.rs

 mod file_system_watcher;
 mod file_tree;
 pub mod network;
+pub mod protocol;
 
 pub use database::Database;
 pub use file_system_watcher::FileSystemWatcher;

src/protocol.rs

+use serde::{Deserialize, Serialize};
+
 /*pub trait Protocol {
     fn login_password(&mut self, user: &str, password: &str) -> Result<String, Error>;
     fn login_app_key(&mut self, user: &str, key: &str) -> Result<(), Error>;
     // TODO
 }*/
 
-pub struct DirectoryListing {
+/*pub struct DirectoryListing {
     own_version: u64,
     entries: Vec<FileMetadata>,
     // TODO
     Directory,
     File,
     SymbolicLink,
-}
+}*/
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct Packet {
-    pub serial_number: u32,
-    pub type_: PacketContent,
+    pub id: u32,
+    pub response: bool,
+    pub payload: PacketPayload,
 }
 
-pub enum PacketContent {
-    Keepalive,
+#[derive(Debug, Deserialize, Serialize)]
+pub enum PacketPayload {
     Error(Error),
     ServerInfo,
-    ServerInfoResponse(ServerInfoResponse,
+    ServerInfoResponse(ServerInfoResponse),
     PasswordLogin(PasswordLogin),
     PasswordLoginResponse(PasswordLoginResponse),
     AppKeyLogin(AppKeyLogin),
     FinishFileUpdate,
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub enum Error {
-    // TODO
+    InvalidParameter,
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct ServerInfoResponse {
     // TODO: Version of the protocol, type of the server (encrypted/unencrypted).
+    pub version: String,
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct PasswordLogin {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct PasswordLoginResponse {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct AppKeyLogin {
     // TODO
 }
+
+#[derive(Debug, Deserialize, Serialize)]
 pub struct AppKeyLoginResponse {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct RegisterInterest {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct RegisterInterestResponse {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct UnregisterInterest {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct UnregisterInterestResponse {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct ListDirectory {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct ListDirectoryResponse {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct GetFileMetadata {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct GetFileMetadataResponse {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct GetFileContent {
     // TODO
 }
 
+#[derive(Debug, Deserialize, Serialize)]
 pub struct GetFileContentResponse {
     // TODO
 }