TCP echo server

gleam.toml

@@ -14,6 +14,8 @@ version = "1.0.0"
 
 [dependencies]
 gleam_stdlib = ">= 0.44.0 and < 2.0.0"
+gleam_otp = ">= 1.2.0 and < 2.0.0"
+gleam_erlang = ">= 1.3.0 and < 2.0.0"
 
 [dev-dependencies]
 gleeunit = ">= 1.0.0 and < 2.0.0"

manifest.toml

@@ -2,10 +2,14 @@
 # You typically do not need to edit this file
 
 packages = [
+  { name = "gleam_erlang", version = "1.3.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_erlang", source = "hex", outer_checksum = "1124AD3AA21143E5AF0FC5CF3D9529F6DB8CA03E43A55711B60B6B7B3874375C" },
+  { name = "gleam_otp", version = "1.2.0", build_tools = ["gleam"], requirements = ["gleam_erlang", "gleam_stdlib"], otp_app = "gleam_otp", source = "hex", outer_checksum = "BA6A294E295E428EC1562DC1C11EA7530DCB981E8359134BEABC8493B7B2258E" },
   { name = "gleam_stdlib", version = "0.65.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "7C69C71D8C493AE11A5184828A77110EB05A7786EBF8B25B36A72F879C3EE107" },
   { name = "gleeunit", version = "1.9.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleeunit", source = "hex", outer_checksum = "DA9553CE58B67924B3C631F96FE3370C49EB6D6DC6B384EC4862CC4AAA718F3C" },
 ]
 
 [requirements]
+gleam_otp = { version = ">= 1.2.0 and < 2.0.0" }
 gleam_stdlib = { version = ">= 0.44.0 and < 2.0.0" }
 gleeunit = { version = ">= 1.0.0 and < 2.0.0" }
+gleam_erlang = { version = ">= 1.3.0 and < 2.0.0" }

src/musicplayer.gleam

@@ -1,11 +1,15 @@
 import gleam/io
 
+import tcp/echo_server
 import tcp/reason
 import tcp/tcp
 
 pub fn main() -> Nil {
   let socket_path = "/tmp/musicplayer.sock"
 
+  case echo_server.new(socket_path) {
+    Error(err) -> io.println("Failed to create echo server: " <> err)
+    Ok(_) -> {
       case tcp.connect(socket_path) {
         Error(r) ->
           io.println("Failed to connect to socket: " <> reason.to_string(r))
@@ -16,11 +20,21 @@ pub fn main() -> Nil {
 
           messages |> send_messages(socket, _)
 
+          case tcp.receive(socket) {
+            Error(r) ->
+              io.println(
+                "Failed to receive from socket: " <> reason.to_string(r),
+              )
+            Ok(data) -> io.println("Recieved: " <> data)
+          }
+
           io.println("closing")
           tcp.close(socket)
         }
       }
     }
+  }
+}
 
 fn send_messages(socket: tcp.Socket, messages: List(String)) -> Nil {
   case messages {

src/tcp/echo_server.gleam

@@ -0,0 +1,39 @@
+import gleam/otp/actor
+import tcp/reason
+
+import tcp/tcp
+
+pub type Message {
+  Shutdown
+  ReadyToAccept(listen_socket: tcp.Socket)
+}
+
+pub fn new(socket_path: String) -> Result(Nil, String) {
+  let server = actor.new(Nil) |> actor.on_message(handle_message) |> actor.start
+
+  case tcp.listen(socket_path), server {
+    Ok(socket), Ok(b) -> {
+      let server = b.data
+      actor.send(server, ReadyToAccept(socket))
+      Ok(Nil)
+    }
+    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")
+      }
+  }
+}
+
+fn handle_message(_: Nil, message: Message) -> actor.Next(Nil, Message) {
+  case message {
+    Shutdown -> actor.stop()
+
+    ReadyToAccept(_) -> {
+      // TODO tcp.accept
+      actor.continue(Nil)
+    }
+  }
+}

src/tcp/tcp.gleam

@@ -1,4 +1,6 @@
+import gleam/bit_array
 import gleam/bytes_tree
+import gleam/result
 
 import tcp/reason.{type Reason}
 
@@ -17,15 +19,52 @@ type ModeValue {
 type TCPOption {
   Active(Bool)
   Mode(ModeValue)
+  Ifaddr(Local)
+}
+
+pub fn listen(socket_path: String) -> Result(Socket, Reason) {
+  // TODO maybe reuseaddr?
+  let options = [Mode(Binary), Active(False), Ifaddr(Local(socket_path))]
+  // port zero with `local` address
+  let port = 0
+
+  gen_tcp_listen(port, options)
+}
+
+pub fn accept(socket: Socket) -> Result(Socket, Reason) {
+  gen_tcp_accept(socket)
+}
+
+pub fn receive(socket: Socket) -> Result(String, Reason) {
+  // Get all bytes
+  let length = 0
+
+  // timeout in ms
+  let timeout = 1000
+
+  result.try(gen_tcp_recv(socket, length, timeout), fn(bt) {
+    case
+      bt
+      |> bytes_tree.to_bit_array
+      |> bit_array.to_string
+    {
+      // TODO what error?
+      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) {
@@ -36,6 +75,22 @@ pub fn close(socket: Socket) -> Nil {
   gen_tcp_close(socket)
 }
 
+// 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(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(bytes_tree.BytesTree, Reason)
+
 // https://www.erlang.org/doc/apps/kernel/gen_tcp.html#connect/4
 @external(erlang, "gen_tcp", "connect")
 fn gen_tcp_connect(