diff --git a/src/lib_p2p/p2p.ml b/src/lib_p2p/p2p.ml
index dc335c99efd09c6b64d1ec897f13f4e7e673a5bc..2b040b71465644282ce36a726334b05d66fa3504 100644
--- a/src/lib_p2p/p2p.ml
+++ b/src/lib_p2p/p2p.ml
@@ -54,7 +54,7 @@ let create_scheduler limits =
     ?write_queue_size:limits.write_queue_size
     ()
 
-let create_connection_pool config limits meta_cfg log triggers =
+let create_connection_pool ?fd_pool config limits meta_cfg log triggers =
   let open P2p_limits in
   let pool_cfg =
     {
@@ -69,7 +69,7 @@ let create_connection_pool config limits meta_cfg log triggers =
       ip_greylist_cleanup_delay = limits.ip_greylist_cleanup_delay;
     }
   in
-  P2p_pool.create pool_cfg meta_cfg ~log triggers
+  P2p_pool.create ?fd_pool pool_cfg meta_cfg ~log triggers
 
 let create_connect_handler config limits pool msg_cfg conn_meta_cfg io_sched
     triggers log answerer =
@@ -188,14 +188,16 @@ module Real = struct
 
   let pool net = P2p_connect_handler.get_pool net.connect_handler
 
-  let create ~config ~limits ?received_msg_hook ?sent_msg_hook
+  let create ?fd_pool ~config ~limits ?received_msg_hook ?sent_msg_hook
       ?broadcasted_msg_hook meta_cfg msg_cfg conn_meta_cfg =
     let open Lwt_result_syntax in
     let io_sched = create_scheduler limits in
     let watcher = Lwt_watcher.create_input () in
     let log event = Lwt_watcher.notify watcher event in
     let triggers = P2p_trigger.create () in
-    let*! pool = create_connection_pool config limits meta_cfg log triggers in
+    let*! pool =
+      create_connection_pool ?fd_pool config limits meta_cfg log triggers
+    in
     (* There is a mutual recursion between an answerer and connect_handler,
        for the default answerer. Because of the swap request mechanism, the
        default answerer needs to initiate new connections using the
@@ -601,12 +603,13 @@ let check_limits =
     in
     return_unit
 
-let create ~config ~limits ?received_msg_hook ?sent_msg_hook
+let create ?fd_pool ~config ~limits ?received_msg_hook ?sent_msg_hook
     ?broadcasted_msg_hook peer_cfg conn_cfg msg_cfg =
   let open Lwt_result_syntax in
   let*? () = check_limits limits in
   let* net =
     Real.create
+      ?fd_pool
       ~config
       ~limits
       ?received_msg_hook
diff --git a/src/lib_p2p/p2p.mli b/src/lib_p2p/p2p.mli
index f6d083b3e0c13a2e552c21ea1d3a6f18cba13967..489f660ce8e27cfca3e76cc69d034efdd48c89f7 100644
--- a/src/lib_p2p/p2p.mli
+++ b/src/lib_p2p/p2p.mli
@@ -150,6 +150,7 @@ val faked_network :
     ['msg] is broadcasted.
     *)
 val create :
+  ?fd_pool:P2p_fd.fd_pool ->
   config:config ->
   limits:Tezos_p2p_services.P2p_limits.t ->
   ?received_msg_hook:(('msg, 'peer_meta, 'conn_meta) connection -> 'msg -> unit) ->
diff --git a/src/lib_p2p/p2p_connect_handler.ml b/src/lib_p2p/p2p_connect_handler.ml
index 8a3ac05095150ded1ee1a305e062e3c6cd8ce960..3a167c5a83ec18e5622838fea4dd2cc90918f0a1 100644
--- a/src/lib_p2p/p2p_connect_handler.ml
+++ b/src/lib_p2p/p2p_connect_handler.ml
@@ -719,7 +719,8 @@ let connect ?trusted ?expected_peer_id ?timeout t point =
       let* () = fail_unless_disconnected_point point_info in
       let timestamp = Time.System.now () in
       P2p_point_state.set_requested ~timestamp point_info canceler ;
-      let*! fd = P2p_fd.socket () in
+      let fd_pool = P2p_pool.get_fd_pool t.pool in
+      let* fd = P2p_fd.socket ?fd_pool () in
       P2p_fd.set_point ~point fd ;
       let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
       let*! () = Events.(emit connect_status) ("start", point) in
diff --git a/src/lib_p2p/p2p_fd.ml b/src/lib_p2p/p2p_fd.ml
index 5ee6d98a88ec8be0537d96e5d6ed4c5b4865a930..0baef60b4ff4c335eeeb43207e42d361ca88ddcb 100644
--- a/src/lib_p2p/p2p_fd.ml
+++ b/src/lib_p2p/p2p_fd.ml
@@ -36,7 +36,9 @@ type listening_socket_open_failure = {
   port : int;
 }
 
-type error += Failed_to_open_listening_socket of listening_socket_open_failure
+type error +=
+  | Failed_to_open_listening_socket of listening_socket_open_failure
+  | Full_waiting_queue
 
 let () =
   register_error_kind
@@ -76,7 +78,20 @@ let () =
           Some (reason, address, port)
       | _ -> None)
     (fun (reason, address, port) ->
-      Failed_to_open_listening_socket {reason; address; port})
+      Failed_to_open_listening_socket {reason; address; port}) ;
+  let description =
+    "Not only the maximum number of connection has been reached, but the \
+     waiting queue for connections is already full."
+  in
+  register_error_kind
+    `Permanent
+    ~id:"p2p.fd.Full_waiting_queue"
+    ~title:"Connection rejected since waiting queue is full"
+    ~description
+    ~pp:(fun ppf () -> Format.fprintf ppf "%s" description)
+    Data_encoding.empty
+    (function Full_waiting_queue -> Some () | _ -> None)
+    (fun () -> Full_waiting_queue)
 
 let is_not_windows = Sys.os_type <> "Win32"
 
@@ -103,11 +118,21 @@ type connect_error =
   | unexpected_error ]
 
 type accept_error =
-  [`System_error of exn | `Socket_error of exn | unexpected_error]
+  [ `System_error of exn
+  | `Socket_error of exn
+  | `Full_waiting_queue
+  | unexpected_error ]
+
+let accept_error_to_tzerror = function
+  | `System_error exn | `Socket_error exn | `Unexpected_error exn ->
+      error_of_exn exn
+  | `Full_waiting_queue -> Full_waiting_queue
 
 type t = {
   fd : Lwt_unix.file_descr;
   id : int;
+  wakener : unit Lwt.u option;
+      (** Used to put the token back in the fd_pool after closing the file descriptor. *)
   mutable point : P2p_point.Id.t option;
   mutable peer_id : P2p_peer.Id.t option;
   mutable nread : int;
@@ -115,6 +140,10 @@ type t = {
   mutable closing_reasons : P2p_disconnection_reason.t list;
 }
 
+type fd_pool = unit Lwt_pool.t
+
+let create_fd_pool ~capacity = Lwt_pool.create capacity Lwt.return
+
 let set_point ~point t = t.point <- Some point
 
 let set_peer_id ~peer_id t = t.peer_id <- Some peer_id
@@ -138,8 +167,26 @@ let pp_read_write_error fmt = function
 
 let create =
   let counter = ref 0 in
-  fun fd ->
-    let open Lwt_syntax in
+  fun ?fd_pool fd ->
+    let open Lwt_result_syntax in
+    let* wakener =
+      match fd_pool with
+      | None -> return None
+      | Some fd_pool ->
+          (* [1000] is quite arbitrary. It is chosen to be in the same range as
+             the typical pools. The pools are expected to be around 1000
+             as the number of opened file descriptors on Linux is limited to 1024. *)
+          if Lwt_pool.wait_queue_length fd_pool > 1000 then
+            Lwt_result.fail `Full_waiting_queue
+          else
+            let p, u = Lwt.task () in
+            (* We grab an element of the pool, which will be freed only when
+               [u] will be waken up. *)
+            let _ : unit Lwt.t = Lwt_pool.use fd_pool (fun () -> p) in
+            (* We wait until the pool is not full. *)
+            let* () = Lwt_pool.use fd_pool return in
+            return (Some u)
+    in
     incr counter ;
     let t =
       {
@@ -150,9 +197,10 @@ let create =
         nread = 0;
         nwrit = 0;
         closing_reasons = [];
+        wakener;
       }
     in
-    let* () = Events.(emit create_fd) t.id in
+    let*! () = Events.(emit create_fd) t.id in
     return t
 
 let string_of_sockaddr addr =
@@ -258,10 +306,12 @@ let raw_socket () =
   let* sock = socket_setopt_user_timeout sock in
   socket_setopt_keepalive sock
 
-let socket () =
+let socket ?fd_pool () =
   let open Lwt_syntax in
   let* socket = raw_socket () in
-  create socket
+  Lwt_result.map_error
+    (fun `Full_waiting_queue -> [Full_waiting_queue])
+    (create ?fd_pool socket)
 
 let create_listening_socket ?(reuse_port = false) ~backlog
     ?(addr = Ipaddr.V6.unspecified) port =
@@ -326,7 +376,12 @@ let close ?reason t =
   Lwt.catch
     (fun () ->
       (* Guarantee idempotency. *)
-      if Lwt_unix.state t.fd = Closed then return_unit else close_socket t.fd)
+      if Lwt_unix.state t.fd = Closed then return_unit
+      else
+        let open Lwt_syntax in
+        let* () = close_socket t.fd in
+        Option.iter (fun wakener -> Lwt.wakeup wakener ()) t.wakener ;
+        return_unit)
     (function
       (* From [man 2 close] [close] can fail with [EBADF, EINTR, EIO, ENOSPC,
          EDQUOT] Unix errors.
@@ -439,7 +494,7 @@ let connect t saddr =
           in
           Lwt.return_error (`Unexpected_error ex))
 
-let accept listening_socket =
+let accept ?fd_pool listening_socket =
   let open Lwt_result_syntax in
   let* fd, saddr =
     Lwt.catch
@@ -482,7 +537,7 @@ let accept listening_socket =
             Lwt.return_error @@ `Socket_error e
         | ex -> Lwt.return_error @@ `Unexpected_error ex)
   in
-  let*! t = create fd in
+  let* t = create ?fd_pool fd in
   let*! () = Events.(emit accept_fd) (t.id, string_of_sockaddr saddr) in
   return (t, saddr)
 
diff --git a/src/lib_p2p/p2p_fd.mli b/src/lib_p2p/p2p_fd.mli
index db5cff2c8ca7cc887d74687ade0c5918d7a158ee..7194f8e327b152b02a6676b38eb7bb8860ddbba4 100644
--- a/src/lib_p2p/p2p_fd.mli
+++ b/src/lib_p2p/p2p_fd.mli
@@ -32,7 +32,9 @@ type listening_socket_open_failure = {
 
 (** Type of an error in case of the listening
     socket fails to open. *)
-type error += Failed_to_open_listening_socket of listening_socket_open_failure
+type error +=
+  | Failed_to_open_listening_socket of listening_socket_open_failure
+  | Full_waiting_queue
 
 (** This module defines a type [t] which wraps a file descriptor. Most
     functions simply call the underlying file descriptor function and generate
@@ -66,7 +68,7 @@ type read_write_error =
   | `Connection_locally_closed
   | unexpected_error ]
 
-(** 
+(**
 
    - Unreachable can be issued when we don't know how to reach to this address
 
@@ -77,7 +79,7 @@ type read_write_error =
    the behaviour of the firewall: If the firewall drops packets, it
    will be canceled because of a timeout, otherwise it can refuse the
    connection and we get this error.
-   
+
 *)
 
 type connect_error =
@@ -101,7 +103,12 @@ type connect_error =
     For most socket-errors you can just log them and call accept again to be
     ready for the next connection. *)
 type accept_error =
-  [`System_error of exn | `Socket_error of exn | unexpected_error]
+  [ `System_error of exn
+  | `Socket_error of exn
+  | `Full_waiting_queue
+  | unexpected_error ]
+
+val accept_error_to_tzerror : accept_error -> error
 
 (** Pretty printer for read_write_error. *)
 val pp_read_write_error : Format.formatter -> read_write_error -> unit
@@ -136,8 +143,19 @@ val read : t -> Bytes.t -> int -> int -> (int, read_write_error) result Lwt.t
     underlying socket has been closed. *)
 val write : t -> Bytes.t -> (unit, read_write_error) result Lwt.t
 
-(** Returns a fresh fd. This call always succeed. *)
-val socket : unit -> t Lwt.t
+(** [fd_pool] is the type of file descriptors pool used to control the number
+    of connections opened simultaneously. *)
+type fd_pool
+
+(** [create_fd_pool capacity] creates a file descriptors pool accepting at most
+    [capacity] connections. *)
+val create_fd_pool : capacity:int -> fd_pool
+
+(** [socket ?fd_pool ()] returns a fresh fd.
+    If [fd_pool] is [None], this call succeeds immediatly.
+    If [fd_pool] is [Some p], it waits until [p] has a free element which
+    can be taken, and succeds. *)
+val socket : ?fd_pool:fd_pool -> unit -> t tzresult Lwt.t
 
 (** [create_listening_socket ?reuse_port ~backlog ?addr port] creates
     a socket that listens on [addr] or [Ipaddr.V6.unspecified] if
@@ -159,8 +177,13 @@ val create_listening_socket :
     closed. *)
 val connect : t -> Lwt_unix.sockaddr -> (unit, connect_error) result Lwt.t
 
-(** [accept sock] accepts connections on socket [sock]. *)
+(** [accept ?fd_pool sock] accepts connections on socket [sock].
+    If [fd_pool] is [None], it does not perform more checks.
+    If [fd_pool] is [Some p], it waits until [p] has a free element which
+    can be taken, and succeeds. *)
 val accept :
-  Lwt_unix.file_descr -> (t * Lwt_unix.sockaddr, accept_error) result Lwt.t
+  ?fd_pool:fd_pool ->
+  Lwt_unix.file_descr ->
+  (t * Lwt_unix.sockaddr, accept_error) result Lwt.t
 
 module Table : Hashtbl.S with type key = t
diff --git a/src/lib_p2p/p2p_pool.ml b/src/lib_p2p/p2p_pool.ml
index 722640bccda5bb23b2fe0925b6ac6d9dec1605a9..a9c6a12d9bf2fa22d861716c5d3a54ff50dadd3c 100644
--- a/src/lib_p2p/p2p_pool.ml
+++ b/src/lib_p2p/p2p_pool.ml
@@ -73,8 +73,11 @@ type ('msg, 'peer, 'conn) t = {
   triggers : P2p_trigger.t;
   log : P2p_connection.P2p_event.t -> unit;
   acl : P2p_acl.t;
+  fd_pool : P2p_fd.fd_pool option;
 }
 
+let get_fd_pool t = t.fd_pool
+
 module Gc_point_set = Bounded_heap.Make (struct
   type t = Time.System.t * P2p_point.Id.t
 
@@ -551,7 +554,7 @@ let score {peer_meta_config = {score; _}; _} meta = score meta
 
 let active_connections pool = P2p_peer.Table.length pool.connected_peer_ids
 
-let create config peer_meta_config triggers ~log =
+let create ?fd_pool config peer_meta_config triggers ~log =
   let open Lwt_syntax in
   let pool =
     {
@@ -569,6 +572,7 @@ let create config peer_meta_config triggers ~log =
           ~ip_size:config.ip_greylist_size_in_kilobytes
           ~ip_cleanup_delay:config.ip_greylist_cleanup_delay;
       log;
+      fd_pool;
     }
   in
   List.iter (Points.set_trusted pool) config.trusted_points ;
@@ -743,7 +747,7 @@ module Internal_for_tests = struct
       ip_greylist_cleanup_delay;
     }
 
-  let create peer_meta_encoding initial_peer =
+  let create ?fd_pool peer_meta_encoding initial_peer =
     let triggers = P2p_trigger.create () in
     let config = dumb_config in
     let peer_meta_config : 'peer P2p_params.peer_meta_config =
@@ -770,5 +774,6 @@ module Internal_for_tests = struct
           ~ip_size:config.ip_greylist_size_in_kilobytes
           ~ip_cleanup_delay:config.ip_greylist_cleanup_delay;
       log;
+      fd_pool;
     }
 end
diff --git a/src/lib_p2p/p2p_pool.mli b/src/lib_p2p/p2p_pool.mli
index 2870df1c52b3114bc5ac99de2dcadd5a22fb1b4d..f2eb640f01f95a892ae9bd618903dcf1a0bc3398 100644
--- a/src/lib_p2p/p2p_pool.mli
+++ b/src/lib_p2p/p2p_pool.mli
@@ -72,6 +72,7 @@ type config = {
 }
 
 val create :
+  ?fd_pool:P2p_fd.fd_pool ->
   config ->
   'peer P2p_params.peer_meta_config ->
   P2p_trigger.t ->
@@ -429,10 +430,19 @@ val add_to_id_points : ('msg, 'peer, 'conn) t -> P2p_point.Id.t -> unit
 val set_expected_peer_id :
   ('msg, 'peer, 'conn) t -> P2p_point.Id.t -> P2p_peer.Id.t -> unit Lwt.t
 
+(** [get_fd_pool t] returns the file descriptors pool contained in [t], if any.*)
+val get_fd_pool : ('msg, 'peer, 'conn) t -> P2p_fd.fd_pool option
+
 (**/**)
 
 module Internal_for_tests : sig
-  (** [create peer_encoding peer] returns a pool. [peer_encoding] and [peer] are needed as some functions of [P2p_pool]
-      return it. *)
-  val create : 'peer Data_encoding.t -> 'peer -> ('msg, 'peer, 'conn) t
+  (** [create ?fd_pool peer_encoding peer] returns a pool.
+     [peer_encoding] and [peer] are needed as some functions of [P2p_pool]
+     return it.
+     [fd_pool] is the field containing the file descriptors pool of the constructed pool.*)
+  val create :
+    ?fd_pool:P2p_fd.fd_pool ->
+    'peer Data_encoding.t ->
+    'peer ->
+    ('msg, 'peer, 'conn) t
 end
diff --git a/src/lib_p2p/p2p_socket.ml b/src/lib_p2p/p2p_socket.ml
index 9b5f9980da5e74183f30b0187c91c44ed5636f58..4dd172b33d4f44ba1824cbece518da98ddb339f5 100644
--- a/src/lib_p2p/p2p_socket.ml
+++ b/src/lib_p2p/p2p_socket.ml
@@ -908,7 +908,11 @@ module Internal_for_tests = struct
         }
     in
     let scheduled_conn =
-      let f2d_t = Tezos_base_unix.Event_loop.main_run P2p_fd.socket in
+      let socket = Tezos_base_unix.Event_loop.main_run P2p_fd.socket in
+      let f2d_t =
+        match socket with Ok socket -> socket | Error _ -> assert false
+        (* [P2p_fd.socket] cannot fail when not given a fd_pool. *)
+      in
       P2p_io_scheduler.register
         (P2p_io_scheduler.create ~read_buffer_size:0 ())
         f2d_t
diff --git a/src/lib_p2p/p2p_welcome.ml b/src/lib_p2p/p2p_welcome.ml
index abd7ec1655b2836f9bd083795d42e44a0fedc725..7c21a69c5539272076a7bc38a291f3597bc894c0 100644
--- a/src/lib_p2p/p2p_welcome.ml
+++ b/src/lib_p2p/p2p_welcome.ml
@@ -47,7 +47,10 @@ let accept st =
   let* () = Lwt_mutex.lock accept_lock in
   let* res =
     protect @@ fun () ->
-    let* r = P2p_fd.accept st.socket in
+    let fd_pool =
+      P2p_pool.get_fd_pool @@ P2p_connect_handler.get_pool connect_handler
+    in
+    let* r = P2p_fd.accept ?fd_pool st.socket in
     Result.fold
       ~ok:(fun (fd, addr) ->
         let point =
@@ -77,10 +80,7 @@ let accept st =
                 (TzTrace.make (error_of_exn ex), "socket")
             in
             Lwt.return (Ok ())
-        | `Unexpected_error ex ->
-            (* TODO: https://gitlab.com/tezos/tezos/-/issues/5632
-               Losing some information here... *)
-            Lwt.return_error (TzTrace.make (error_of_exn ex)))
+        | ex -> Lwt_result_syntax.tzfail (P2p_fd.accept_error_to_tzerror ex))
       r
   in
   Lwt_mutex.unlock accept_lock ;
diff --git a/src/lib_p2p/test/common/p2p_test_utils.ml b/src/lib_p2p/test/common/p2p_test_utils.ml
index 282858cbcdfd0af873fa91cf5aac57303ded5857..c9f47469d661ec178f39c6750ed6a589fea795f7 100644
--- a/src/lib_p2p/test/common/p2p_test_utils.ml
+++ b/src/lib_p2p/test/common/p2p_test_utils.ml
@@ -264,8 +264,7 @@ let raw_accept sched main_socket =
   let open Lwt_syntax in
   let* r = P2p_fd.accept main_socket in
   match r with
-  | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-      Lwt.fail ex
+  | Error e -> Lwt_result_syntax.tzfail (P2p_fd.accept_error_to_tzerror e)
   | Ok (fd, sockaddr) ->
       let fd = P2p_io_scheduler.register sched fd in
       let point =
@@ -285,8 +284,7 @@ let accept ?(id = id1) ?(proof_of_work_target = proof_of_work_target) sched
   let* r = raw_accept sched main_socket in
   let* id1 = id in
   match r with
-  | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-      Lwt.fail ex
+  | Error e -> Lwt_result.fail e
   | Ok (fd, point) ->
       P2p_socket.authenticate
         ~canceler
@@ -300,11 +298,11 @@ let accept ?(id = id1) ?(proof_of_work_target = proof_of_work_target) sched
 
 let raw_connect sched addr port =
   let open Lwt_result_syntax in
-  let*! fd = P2p_fd.socket () in
+  let* fd = Lwt_result.map_error Either.right (P2p_fd.socket ()) in
   let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
-  let* () = P2p_fd.connect fd uaddr in
+  let* () = Lwt_result.map_error Either.left (P2p_fd.connect fd uaddr) in
   let fd = P2p_io_scheduler.register sched fd in
-  Lwt.return_ok fd
+  return fd
 
 exception Cant_connect
 
@@ -316,9 +314,11 @@ let connect ?(proof_of_work_target = proof_of_work_target) sched addr port id =
   let*! r = raw_connect sched addr port in
   match r with
   | Error
-      ( `Network_unreachable | `Connection_unreachable | `Connection_refused
-      | `Connection_canceled | `Unexpected_error _ ) ->
+      (Left
+        ( `Network_unreachable | `Connection_unreachable | `Connection_refused
+        | `Connection_canceled | `Unexpected_error _ )) ->
       Lwt.fail Cant_connect
+  | Error (Right e) -> Lwt_result.fail e
   | Ok fd ->
       P2p_socket.authenticate
         ~canceler
diff --git a/src/lib_p2p/test/common/p2p_test_utils.mli b/src/lib_p2p/test/common/p2p_test_utils.mli
index ec868525c1f1543df3f0b672d41e1a0cdf3116da..894dd95ddd85d629e0040ac36e14077dd8c63824 100644
--- a/src/lib_p2p/test/common/p2p_test_utils.mli
+++ b/src/lib_p2p/test/common/p2p_test_utils.mli
@@ -111,8 +111,7 @@ val run_nodes_fd :
 val raw_accept :
   P2p_io_scheduler.t ->
   Lwt_unix.file_descr ->
-  (P2p_io_scheduler.connection * (P2p_addr.t * int), P2p_fd.accept_error) result
-  Lwt.t
+  (P2p_io_scheduler.connection * (P2p_addr.t * int)) tzresult Lwt.t
 
 val accept :
   ?id:P2p_identity.t Lwt.t ->
@@ -128,7 +127,8 @@ val raw_connect :
   P2p_io_scheduler.t ->
   P2p_addr.t ->
   int ->
-  (P2p_io_scheduler.connection, P2p_fd.connect_error) result Lwt.t
+  (P2p_io_scheduler.connection, (P2p_fd.connect_error, tztrace) Either.t) result
+  Lwt.t
 
 val connect :
   ?proof_of_work_target:Tezos_crypto.Crypto_box.pow_target ->
diff --git a/src/lib_p2p/test/test_p2p_connect_handler.ml b/src/lib_p2p/test/test_p2p_connect_handler.ml
index 349d3fb98dd948a53e2b31937ccc21a236e0ce32..9144cfc4cb9bc213dbba6591e54d52f22f233505 100644
--- a/src/lib_p2p/test/test_p2p_connect_handler.ml
+++ b/src/lib_p2p/test/test_p2p_connect_handler.ml
@@ -84,7 +84,7 @@ let test_correct_incoming_connection_number =
       (`Make_default_pool ())
       (`Dependencies dependencies)
   in
-  let*! fd = P2p_fd.socket () in
+  let* fd = P2p_fd.socket () in
   Alcotest.(
     check'
       int
diff --git a/src/lib_p2p/test/test_p2p_io_scheduler.ml b/src/lib_p2p/test/test_p2p_io_scheduler.ml
index 2734734878827e4ab43a8ce5859cd0a6b72135ef..6c03e99b413d16b75991194d30c6cf7fb05ecdca 100644
--- a/src/lib_p2p/test/test_p2p_io_scheduler.ml
+++ b/src/lib_p2p/test/test_p2p_io_scheduler.ml
@@ -50,15 +50,14 @@ let rec listen ?port addr =
   | Error err -> Lwt.return_error err
 
 let accept main_socket =
-  let open Lwt_syntax in
-  let* r = P2p_fd.accept main_socket in
+  let open Lwt_result_syntax in
+  let*! r = P2p_fd.accept main_socket in
   match r with
-  | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-      Lwt.fail ex
-  | Ok (fd, _) -> Lwt.return fd
+  | Error e -> tzfail (P2p_fd.accept_error_to_tzerror e)
+  | Ok (fd, _) -> return fd
 
 let rec accept_n main_socket n =
-  let open Lwt_syntax in
+  let open Lwt_result_syntax in
   if n <= 0 then return_nil
   else
     let* acc = accept_n main_socket (n - 1) in
@@ -68,6 +67,13 @@ let rec accept_n main_socket n =
 let connect addr port =
   let open Lwt_syntax in
   let* fd = P2p_fd.socket () in
+  let fd =
+    match fd with
+    | Ok fd -> fd
+    | Error _ ->
+        assert
+          false (* [P2p_fd.socket] cannot fail when not given a fd_semaphore. *)
+  in
   let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
   let* r = P2p_fd.connect fd uaddr in
   match r with
@@ -107,7 +113,7 @@ let receive conn =
 
 let server ?(display_client_stat = true) ?max_download_speed ?read_queue_size
     ~read_buffer_size main_socket n =
-  let open Lwt_syntax in
+  let open Lwt_result_syntax in
   let sched =
     P2p_io_scheduler.create
       ?max_download_speed
@@ -127,8 +133,10 @@ let server ?(display_client_stat = true) ?max_download_speed ?read_queue_size
   (* Accept and read message until the connection is closed. *)
   let* conns = accept_n main_socket n in
   let conns = List.map (P2p_io_scheduler.register sched) conns in
-  let* () = List.iter_p receive (List.map P2p_io_scheduler.to_readable conns) in
-  let* r =
+  let*! () =
+    List.iter_p receive (List.map P2p_io_scheduler.to_readable conns)
+  in
+  let*! r =
     List.iter_ep
       (P2p_io_scheduler.close ~reason:(User "shutdown from server"))
       conns
@@ -136,7 +144,7 @@ let server ?(display_client_stat = true) ?max_download_speed ?read_queue_size
   match r with
   | Ok () ->
       Tezt.Log.debug "OK %a" P2p_stat.pp (P2p_io_scheduler.global_stat sched) ;
-      return_ok ()
+      return ()
   | Error _ -> Lwt.fail Alcotest.Test_error
 
 let max_size ?max_upload_speed () =
diff --git a/src/lib_p2p/test/test_p2p_socket.ml b/src/lib_p2p/test/test_p2p_socket.ml
index 808d10c266b812f713953b7365465d76df4f1845..c5ae7fbb7f1fa193fbb4eca1712a68909383fbce 100644
--- a/src/lib_p2p/test/test_p2p_socket.ml
+++ b/src/lib_p2p/test/test_p2p_socket.ml
@@ -224,10 +224,7 @@ module Low_level = struct
     let msg = Bytes.create (Bytes.length simple_msg) in
     let*! r = raw_connect sched addr port in
     match r with
-    | Error
-        ( `Network_unreachable | `Connection_unreachable | `Connection_refused
-        | `Connection_canceled | `Unexpected_error _ ) ->
-        Lwt.fail Alcotest.Test_error
+    | Error _ -> Lwt.fail Alcotest.Test_error
     | Ok fd ->
         let* () =
           P2p_buffer_reader.(
@@ -241,8 +238,7 @@ module Low_level = struct
     let open Lwt_result_syntax in
     let*! r = raw_accept sched socket in
     match r with
-    | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-        Lwt.fail ex
+    | Error e -> fail e
     | Ok (fd, _point) ->
         let* () = P2p_io_scheduler.write fd simple_msg in
         let* () = sync ch in
diff --git a/src/lib_p2p/tezt/test_p2p_fd.ml b/src/lib_p2p/tezt/test_p2p_fd.ml
index cdfc6a294c8cd8afa8c9c4f365a88d0beb20285f..63660ae06fd466bed606d5b62a1028f927621a5d 100644
--- a/src/lib_p2p/tezt/test_p2p_fd.ml
+++ b/src/lib_p2p/tezt/test_p2p_fd.ml
@@ -37,13 +37,12 @@ let test_connect () =
   let server _ch listening_fd =
     let*! r = P2p_fd.accept listening_fd in
     match r with
-    | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-        Lwt.return_error (TzTrace.make (error_of_exn ex))
+    | Error e -> tzfail (P2p_fd.accept_error_to_tzerror e)
     | Ok (_fd, _sockaddr) -> return_unit
   in
 
   let client _ch addr port =
-    let*! fd = P2p_fd.socket () in
+    let* fd = P2p_fd.socket () in
     let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
     let*! r = P2p_fd.connect fd uaddr in
     match r with
@@ -80,8 +79,7 @@ let test_read_write () =
   let server data _ch listening_fd =
     let*! r = P2p_fd.accept listening_fd in
     match r with
-    | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-        Lwt.return_error (TzTrace.make (error_of_exn ex))
+    | Error e -> tzfail (P2p_fd.accept_error_to_tzerror e)
     | Ok (fd, _sockaddr) -> (
         let*! r = P2p_fd.write fd data in
         match r with
@@ -95,7 +93,7 @@ let test_read_write () =
   in
 
   let client data _ch addr port =
-    let*! fd = P2p_fd.socket () in
+    let* fd = P2p_fd.socket () in
     let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
     let*! r = P2p_fd.connect fd uaddr in
     match r with
@@ -156,8 +154,7 @@ let test_closed_by_peer_read_outgoing () =
   let server ch listening_fd =
     let*! r = P2p_fd.accept listening_fd in
     match r with
-    | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-        Lwt.return_error (TzTrace.make (error_of_exn ex))
+    | Error e -> tzfail (P2p_fd.accept_error_to_tzerror e)
     | Ok (fd, _sockaddr) ->
         let*! () = P2p_fd.close ~reason:(User "server explicit close") fd in
         let* () = sync ch in
@@ -165,7 +162,7 @@ let test_closed_by_peer_read_outgoing () =
   in
 
   let client ch addr port =
-    let*! fd = P2p_fd.socket () in
+    let* fd = P2p_fd.socket () in
     let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
     let*! r = P2p_fd.connect fd uaddr in
     match r with
@@ -215,8 +212,7 @@ let test_closed_by_peer_read_incoming () =
   let server ch listening_fd =
     let*! r = P2p_fd.accept listening_fd in
     match r with
-    | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-        Lwt.return_error (TzTrace.make (error_of_exn ex))
+    | Error e -> tzfail (P2p_fd.accept_error_to_tzerror e)
     | Ok (fd, _sockaddr) -> (
         let* () = sync ch in
         let data_length = 10 in
@@ -232,7 +228,7 @@ let test_closed_by_peer_read_incoming () =
   in
 
   let client ch addr port =
-    let*! fd = P2p_fd.socket () in
+    let* fd = P2p_fd.socket () in
     let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
     let*! r = P2p_fd.connect fd uaddr in
     match r with
@@ -274,13 +270,12 @@ let test_locally_closed_read_outgoing () =
   let server _ch listening_fd =
     let*! r = P2p_fd.accept listening_fd in
     match r with
-    | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-        Lwt.return_error (TzTrace.make (error_of_exn ex))
+    | Error e -> tzfail (P2p_fd.accept_error_to_tzerror e)
     | Ok (_fd, _sockaddr) -> return_unit
   in
 
   let client _ch addr port =
-    let*! fd = P2p_fd.socket () in
+    let* fd = P2p_fd.socket () in
     let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
     let*! r = P2p_fd.connect fd uaddr in
     match r with
@@ -330,8 +325,7 @@ let test_locally_closed_read_incoming () =
   let server _ch listening_fd =
     let*! r = P2p_fd.accept listening_fd in
     match r with
-    | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-        Lwt.return_error (TzTrace.make (error_of_exn ex))
+    | Error e -> tzfail (P2p_fd.accept_error_to_tzerror e)
     | Ok (fd, _sockaddr) -> (
         let*! () = P2p_fd.close ~reason:(User "server explicit close") fd in
         let data_length = 10 in
@@ -347,7 +341,7 @@ let test_locally_closed_read_incoming () =
   in
 
   let client _ch addr port =
-    let*! fd = P2p_fd.socket () in
+    let* fd = P2p_fd.socket () in
     let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
     let*! r = P2p_fd.connect fd uaddr in
     match r with
@@ -386,13 +380,12 @@ let test_locally_closed_write_outgoing () =
   let server _ch listening_fd =
     let*! r = P2p_fd.accept listening_fd in
     match r with
-    | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-        Lwt.return_error (TzTrace.make (error_of_exn ex))
+    | Error e -> tzfail (P2p_fd.accept_error_to_tzerror e)
     | Ok (_fd, _sockaddr) -> return_unit
   in
 
   let client _ch addr port =
-    let*! fd = P2p_fd.socket () in
+    let* fd = P2p_fd.socket () in
     let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
     let*! r = P2p_fd.connect fd uaddr in
     match r with
@@ -441,8 +434,7 @@ let test_locally_closed_write_incoming () =
   let server _ch listening_fd =
     let*! r = P2p_fd.accept listening_fd in
     match r with
-    | Error (`Socket_error ex | `System_error ex | `Unexpected_error ex) ->
-        Lwt.return_error (TzTrace.make (error_of_exn ex))
+    | Error e -> tzfail (P2p_fd.accept_error_to_tzerror e)
     | Ok (fd, _sockaddr) -> (
         let*! () = P2p_fd.close ~reason:(User "server explicit close") fd in
         let data = Bytes.of_string "test" in
@@ -457,7 +449,7 @@ let test_locally_closed_write_incoming () =
   in
 
   let client _ch addr port =
-    let*! fd = P2p_fd.socket () in
+    let* fd = P2p_fd.socket () in
     let uaddr = Lwt_unix.ADDR_INET (Ipaddr_unix.V6.to_inet_addr addr, port) in
     let*! r = P2p_fd.connect fd uaddr in
     match r with
diff --git a/src/lib_p2p/tezt/test_p2p_socket.ml b/src/lib_p2p/tezt/test_p2p_socket.ml
index 2bc076532fb08baaaf4b40242e050f57b24dc689..84db1e0d1adac1a15fd2a18270e4ae278c25865a 100644
--- a/src/lib_p2p/tezt/test_p2p_socket.ml
+++ b/src/lib_p2p/tezt/test_p2p_socket.ml
@@ -221,7 +221,9 @@ module Self_identification = struct
       in
       let*! conn = P2p_test_utils.raw_connect sched addr port in
       match conn with
-      | Error e -> Test.fail "First connection failed: %a" pp_connect_error e
+      | Error (Left e) ->
+          Test.fail "First connection failed: %a" pp_connect_error e
+      | Error (Right _) -> Test.fail "First connection failed unexpectedly"
       | Ok conn -> (
           let canceler = Lwt_canceler.create () in
           (* During the first connection, the client get the connection message
@@ -240,8 +242,10 @@ module Self_identification = struct
              connection message instead of its own. *)
           let*! conn = P2p_test_utils.raw_connect sched addr port in
           match conn with
-          | Error e ->
+          | Error (Left e) ->
               Test.fail "Second connection failed: %a" pp_connect_error e
+          | Error (Right _) ->
+              Test.fail "Second connection failed: unexpectedly"
           | Ok conn ->
               let canceler = Lwt_canceler.create () in
               let* sent_msg =