TCP echo server

src/musicplayer.gleam

@@ -1,41 +1,5 @@
 import gleam/io
 
-import tcp/reason
-import tcp/tcp
-
 pub fn main() -> Nil {
-  let socket_path = "/tmp/musicplayer.sock"
-
-  case tcp.connect(socket_path) {
-    Error(r) ->
-      io.println("Failed to connect to socket: " <> reason.to_string(r))
-    Ok(socket) -> {
-      io.println("connected")
-
-      let messages = ["hello, \n", "world!\n"]
-
-      messages |> send_messages(socket, _)
-
-      io.println("closing")
-      tcp.close(socket)
-    }
-  }
-}
-
-fn send_messages(socket: tcp.Socket, messages: List(String)) -> Nil {
-  case messages {
-    [] -> Nil
-    [message, ..rest] -> {
-      send_message(socket, message)
-      send_messages(socket, rest)
-    }
-  }
-}
-
-fn send_message(socket: tcp.Socket, message: String) -> Nil {
-  case tcp.send(socket, message) {
-    Error(r) ->
-      io.println("Failed to send message to socket: " <> reason.to_string(r))
-    Ok(_) -> io.println("Sent message to socket")
-  }
+  io.println("musicplayer")
 }

src/tcp/echo_server.gleam

@@ -0,0 +1,81 @@
+import gleam/erlang/process.{type Subject}
+import gleam/io
+import gleam/otp/actor
+import gleam/result
+import gleam/string
+
+import tcp/reason.{type Reason}
+import tcp/tcp
+
+pub type Message {
+  Shutdown
+  ReadyToAccept(subject: Subject(Message), listen_socket: tcp.Socket)
+}
+
+pub fn new(socket_path: String) -> Result(tcp.Socket, String) {
+  let server = actor.new(Nil) |> actor.on_message(handle_message) |> actor.start
+
+  case tcp.listen(socket_path), server {
+    Error(r), _ -> Error(reason.to_string(r))
+    _, Error(start_error) ->
+      case start_error {
+        actor.InitExited(_) -> Error("InitExited")
+        actor.InitFailed(_) -> Error("InitFailed")
+        actor.InitTimeout -> Error("InitTimeout")
+      }
+    Ok(listen_socket), Ok(b) -> {
+      let subject = b.data
+      actor.send(subject, ReadyToAccept(subject, listen_socket))
+      Ok(listen_socket)
+    }
+  }
+}
+
+fn handle_message(_: Nil, message: Message) -> actor.Next(Nil, Message) {
+  case message {
+    Shutdown -> actor.stop()
+
+    ReadyToAccept(subject, listen_socket) -> {
+      case tcp.accept(listen_socket) {
+        Error(r) ->
+          actor.stop_abnormal(
+            "Could not accept connection :" <> reason.to_string(r),
+          )
+        Ok(socket) -> {
+          case receive_from_connection(socket) {
+            Error(r) ->
+              io.println_error(
+                "Failed to receive from connection :" <> reason.to_string(r),
+              )
+            Ok(_) -> Nil
+          }
+
+          actor.send(subject, ReadyToAccept(subject, listen_socket))
+          actor.continue(Nil)
+        }
+      }
+    }
+  }
+}
+
+fn receive_from_connection(socket: tcp.Socket) -> Result(Nil, Reason) {
+  result.try(receive_until_closed(socket, ""), fn(data) {
+    let _ = tcp.send(socket, data)
+    tcp.close(socket)
+    Ok(Nil)
+  })
+}
+
+fn receive_until_closed(
+  socket: tcp.Socket,
+  result: String,
+) -> Result(String, Reason) {
+  case tcp.receive(socket, 10_000) {
+    Error(reason.Closed) -> Ok(result)
+    Error(err) -> Error(err)
+    Ok(data) -> {
+      let result = data |> string.append(result, _)
+      receive_until_closed(socket, result)
+    }
+  }
+}

src/tcp/reason.gleam

@@ -4,6 +4,8 @@ pub type Reason {
   /// from `send`
   Closed
 
+  Overflow
+
   /// Address already in use
   Eaddrinuse
   /// Cannot assign requested address
@@ -158,6 +160,7 @@ pub type Reason {
 
 pub fn to_string(reason: Reason) -> String {
   case reason {
+    Overflow -> "overflow"
     Closed -> "Connection closed (closed)"
     Eacces -> "Permission denied (eacces)"
     Eaddrinuse -> "Address already in use (eaddrinuse)"

src/tcp/tcp.gleam

@@ -1,4 +1,6 @@
-import gleam/bytes_tree
+import gleam/bit_array
+import gleam/erlang/atom
+import gleam/result
 
 import tcp/reason.{type Reason}
 
@@ -17,25 +19,82 @@ type ModeValue {
 type TCPOption {
   Active(Bool)
   Mode(ModeValue)
+  Reuseaddr(Bool)
+  Ifaddr(Local)
+  ExitOnClose(Bool)
+}
+
+pub fn listen(socket_path: String) -> Result(Socket, Reason) {
+  let options = [
+    Mode(Binary),
+    Active(False),
+    Reuseaddr(True),
+    Ifaddr(Local(socket_path)),
+    ExitOnClose(False),
+  ]
+  // port zero with `local` address
+  let port = 0
+
+  gen_tcp_listen(port, options)
+}
+
+pub fn accept(listen_socket: Socket) -> Result(Socket, Reason) {
+  gen_tcp_accept(listen_socket)
+}
+
+pub fn receive(socket: Socket, timeout: Int) -> Result(String, Reason) {
+  // Get all bytes
+  let length = 0
+
+  use bits <- result.try(gen_tcp_recv(socket, length, timeout))
+  case bits |> bit_array.to_string {
+    // TODO what error is best?
+    Error(_) -> Error(reason.Ebadmsg)
+    Ok(s) -> Ok(s)
+  }
 }
 
 pub fn connect(socket_path: String) -> Result(Socket, Reason) {
   let options = [Mode(Binary), Active(False)]
 
+  // port zero with `local` address
+  let port = 0
+
   // timeout in ms
   let timeout = 1000
 
-  gen_tcp_connect(Local(socket_path), 0, options, timeout)
+  gen_tcp_connect(Local(socket_path), port, options, timeout)
 }
 
 pub fn send(socket: Socket, message: String) -> Result(Nil, Reason) {
-  gen_tcp_send(socket, bytes_tree.from_string(message))
+  gen_tcp_send(socket, bit_array.from_string(message))
 }
 
 pub fn close(socket: Socket) -> Nil {
   gen_tcp_close(socket)
 }
 
+pub fn shutdown(socket: Socket) -> Result(Nil, Reason) {
+  let how = atom.create("write")
+  gen_tcp_shutdown(socket, how)
+}
+
+// https://www.erlang.org/doc/apps/kernel/gen_tcp.html#listen/2
+@external(erlang, "gen_tcp", "listen")
+fn gen_tcp_listen(port: Int, option: List(TCPOption)) -> Result(Socket, Reason)
+
+// https://www.erlang.org/doc/apps/kernel/gen_tcp.html#accept/1
+@external(erlang, "gen_tcp", "accept")
+fn gen_tcp_accept(listen_socket: Socket) -> Result(Socket, Reason)
+
+// https://www.erlang.org/doc/apps/kernel/gen_tcp.html#recv/3
+@external(erlang, "gen_tcp", "recv")
+fn gen_tcp_recv(
+  socket: Socket,
+  length: Int,
+  timeout: Int,
+) -> Result(BitArray, Reason)
+
 // https://www.erlang.org/doc/apps/kernel/gen_tcp.html#connect/4
 @external(erlang, "gen_tcp", "connect")
 fn gen_tcp_connect(
@@ -47,11 +106,12 @@ fn gen_tcp_connect(
 
 // https://www.erlang.org/doc/apps/kernel/gen_tcp.html#send/2
 @external(erlang, "tcp_ffi", "send")
-fn gen_tcp_send(
-  socket: Socket,
-  packet: bytes_tree.BytesTree,
-) -> Result(Nil, Reason)
+fn gen_tcp_send(socket: Socket, packet: BitArray) -> Result(Nil, Reason)
 
 // https://www.erlang.org/doc/apps/kernel/gen_tcp.html#close/1
 @external(erlang, "gen_tcp", "close")
 fn gen_tcp_close(socket: Socket) -> Nil
+
+// https://www.erlang.org/doc/apps/kernel/gen_tcp.html#shutdown/2
+@external(erlang, "tcp_ffi", "shutdown")
+fn gen_tcp_shutdown(socket: Socket, how: atom.Atom) -> Result(Nil, Reason)

src/tcp/tcp_ffi.erl

@@ -1,8 +1,14 @@
 -module(tcp_ffi).
--export([send/2]).
+-export([send/2, shutdown/2]).
 
 send(Socket, Packet) ->
   case gen_tcp:send(Socket, Packet) of
     ok -> {ok, nil};
     Res -> Res
   end.
+
+shutdown(Socket, How) ->
+  case gen_tcp:shutdown(Socket, How) of
+    ok -> {ok, nil};
+    Res -> Res
+  end.