docs: convert socket receive docs

4 files changed, 68 insertions, 243 deletions

diff --git a/docs/man/nng_recv.3.adoc b/docs/man/nng_recv.3.adoc
deleted file mode 100644
index ef1f2756..00000000
--- a/docs/man/nng_recv.3.adoc
+++ /dev/null
@@ -1,91 +0,0 @@
-= nng_recv(3)
-//
-// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_recv - recv data
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-int nng_recv(nng_socket s, void *data, size_t *sizep, int flags);
-----
-
-== DESCRIPTION
-
-The `nng_recv()` receives a message.
-
-The _flags_ is a bit mask that may contain any of the following values:
-
-`NNG_FLAG_NONBLOCK`::
-  The function returns immediately, even if no message is available.
-  Without this flag, the function will wait until a message is received
-  by the socket _s_, or any configured timer expires.
-
-`NNG_FLAG_ALLOC`::
-  If this flag is present, then a ((zero-copy)) mode is used.
-  In this case the caller must set the value of _data_ to the location
-  of another pointer (of type `void *`), and the _sizep_ pointer must be set
-  to a location to receive the size of the message body.
-  The function will then allocate a message buffer
-  (as if by xref:nng_alloc.3.adoc[`nng_alloc()`]), fill it with
-  the message body, and store it at the address referenced by _data_, and update
-  the size referenced by _sizep_.
-  The caller is responsible for disposing of the received buffer either by
-  the xref:nng_free.3.adoc[`nng_free()`] function or passing the message (also
-  with the `NNG_FLAG_ALLOC` flag) in a call to xref:nng_send.3.adoc[`nng_send()`].
-
-If the special flag `NNG_FLAG_ALLOC` (see above) is not specified, then the
-caller must set _data_ to a buffer to receive the message body content,
-and must store the size of that buffer at the location pointed to by _sizep_.
-When the function returns, if it is successful, the size at _sizep_ will be
-updated with the actual message body length copied into _data_.
-
-NOTE: The semantics of what receiving a message means vary from protocol to
-protocol, so examination of the protocol documentation is encouraged.
-(For example, with a xref:nng_req.7.adoc[_req_] socket a message may only be received
-after a request has been sent, and a xref:nng_sub.7.adoc[_sub_] socket
-may only receive messages corresponding to topics to which it has subscribed.)
-Furthermore, some protocols may not support receiving data at all, such as
-xref:nng_pub.7.adoc[_pub_].
-
-TIP: The `NNG_FLAG_ALLOC` flag can be used to reduce data copies, thereby
-increasing performance, particularly if the buffer is reused to send
-a response using the same flag.
-
-== RETURN VALUES
-
-This function returns 0 on success, and non-zero otherwise.
-
-== ERRORS
-
-[horizontal]
-`NNG_EAGAIN`:: The operation would block, but `NNG_FLAG_NONBLOCK` was specified.
-`NNG_ECLOSED`:: The socket _s_ is not open.
-`NNG_EINVAL`:: An invalid set of _flags_ was specified.
-`NNG_EMSGSIZE`:: The received message did not fit in the size provided.
-`NNG_ENOMEM`:: Insufficient memory is available.
-`NNG_ENOTSUP`:: The protocol for socket _s_ does not support receiving.
-`NNG_ESTATE`:: The socket _s_ cannot receive data in this state.
-`NNG_ETIMEDOUT`:: The operation timed out.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_alloc.3.adoc[nng_alloc(3)],
-xref:nng_free.3.adoc[nng_free(3)],
-xref:nng_recvmsg.3.adoc[nng_recvmsg(3)],
-xref:nng_send.3.adoc[nng_send(3)],
-xref:nng_strerror.3.adoc[nng_strerror(3)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/man/nng_recv_aio.3.adoc b/docs/man/nng_recv_aio.3.adoc
deleted file mode 100644
index 4c970489..00000000
--- a/docs/man/nng_recv_aio.3.adoc
+++ /dev/null
@@ -1,81 +0,0 @@
-= nng_recv_aio(3)
-//
-// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_recv_aio - receive message asynchronously
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-void nng_recv_aio(nng_socket s, nng_aio *aio);
-----
-
-== DESCRIPTION
-
-The `nng_recv_aio()` receives a xref:nng_msg.5.adoc[message] using the
-xref:nng_socket.5.adoc[socket] _s_ asynchronously.
-
-When a message is successfully received by the socket, it is
-stored in the _aio_ by an internal call equivalent to
-xref:nng_aio_set_msg.3.adoc[`nng_aio_set_msg()`], then the completion
-callback on the _aio_ is executed.
-In this case, xref:nng_aio_result.3.adoc[`nng_aio_result()`] will
-return zero.
-The callback function is responsible for retrieving the message
-and disposing of it appropriately.
-
-IMPORTANT: Failing to accept and dispose of messages in this
-case can lead to memory leaks.
-
-If for some reason the asynchronous receive cannot be completed
-successfully (including by being canceled or timing out), then
-the callback will still be executed,
-but xref:nng_aio_result.3.adoc[`nng_aio_result()`] will be non-zero.
-
-NOTE: The semantics of what receiving a message means varies from protocol to
-protocol, so examination of the protocol documentation is encouraged.
-(For example, with a xref:nng_pub.7.adoc[_pub_] socket the data is broadcast, so that
-any peers who have a suitable subscription will be able to receive it using
-xref:nng_recv.3.adoc[`nng_recv()`] or a similar function.)
-Furthermore, some protocols may not support receiving (such as
-xref:nng_pub.7.adoc[_pub_]) or may require other conditions.
-(For example, xref:nng_req.7.adoc[_req_] sockets cannot normally receive data, which
-are replies to requests, until they have first sent a request.)
-
-== RETURN VALUES
-
-None.  (The operation completes asynchronously.)
-
-== ERRORS
-
-[horizontal]
-`NNG_ECANCELED`:: The operation was aborted.
-`NNG_ECLOSED`:: The socket _s_ is not open.
-`NNG_ENOMEM`:: Insufficient memory is available.
-`NNG_ENOTSUP`:: The protocol for socket _s_ does not support receiving.
-`NNG_ESTATE`:: The socket _s_ cannot receive data in this state.
-`NNG_ETIMEDOUT`:: The receive timeout expired.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_aio_get_msg.3.adoc[nng_aio_get_msg(3)],
-xref:nng_aio_set_msg.3.adoc[nng_aio_set_msg(3)],
-xref:nng_msg_alloc.3.adoc[nng_msg_alloc(3)],
-xref:nng_strerror.3.adoc[nng_strerror(3)],
-xref:nng_aio.5.adoc[nng_aio(5)],
-xref:nng_msg.5.adoc[nng_msg(5)],
-xref:nng_socket.5.adoc[nng_socket(5)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/man/nng_recvmsg.3.adoc b/docs/man/nng_recvmsg.3.adoc
deleted file mode 100644
index c502d650..00000000
--- a/docs/man/nng_recvmsg.3.adoc
+++ /dev/null
@@ -1,71 +0,0 @@
-= nng_recvmsg(3)
-//
-// Copyright 2021 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_recvmsg - receive a message
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-int nng_recvmsg(nng_socket s, nng_msg **msgp, int flags);
-----
-
-== DESCRIPTION
-
-The `nng_recvmsg()` receives a message on socket _s_, storing the
-received message at the location pointed to by _msgp_.
-
-TIP: Using this function gives access to the message structure, and thus may
-offer more functionality than the simpler xref:nng_recv.3.adoc[`nng_recv()`] function.
-
-The _flags_ may contain the following value:
-
-`NNG_FLAG_NONBLOCK`::
-  The function returns immediately, even if no message is available.
-  Without this flag, the function will wait until a message is received
-  by the socket _s_, or any configured timer expires.
-
-NOTE: The semantics of what receiving a message means vary from protocol to
-protocol, so examination of the protocol documentation is encouraged.
-(For example, with an xref:nng_req.7.adoc[_req_] socket a message may only be received
-after a request has been sent, and an xref:nng_sub.7.adoc[_sub_] socket
-may only receive messages corresponding to topics to which it has subscribed.)
-Furthermore, some protocols may not support receiving data at all, such as
-xref:nng_pub.7.adoc[_pub_].
-
-== RETURN VALUES
-
-This function returns 0 on success, and non-zero otherwise.
-
-== ERRORS
-
-[horizontal]
-`NNG_EAGAIN`:: The operation would block, but `NNG_FLAG_NONBLOCK` was specified.
-`NNG_ECLOSED`:: The socket _s_ is not open.
-`NNG_EINVAL`:: An invalid set of _flags_ was specified.
-`NNG_ENOMEM`:: Insufficient memory is available.
-`NNG_ENOTSUP`:: The protocol for socket _s_ does not support receiving.
-`NNG_ESTATE`:: The socket _s_ cannot receive data in this state.
-`NNG_ETIMEDOUT`:: The operation timed out.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_msg_free.3.adoc[nng_msg_free(3)],
-xref:nng_recv.3.adoc[nng_recv(3)],
-xref:nng_sendmsg.3.adoc[nng_sendmsg(3)],
-xref:nng_strerror.3.adoc[nng_strerror(3)],
-xref:nng_socket.5.adoc[nng_socket(5)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/ref/api/sock.md b/docs/ref/api/sock.md
index ede67c3f..54aa6580 100644
--- a/docs/ref/api/sock.md
+++ b/docs/ref/api/sock.md
@@ -227,6 +227,74 @@ For example, the message may be sitting in queue, or located in TCP buffers, or
 > steps on the part of the application, the lowest latencies and highest performance will be achieved by using
 > this function instead of [`nng_send`] or [`nng_sendmsg`].
 
+## Receiving Messages
+
+```c
+int nng_recv(nng_socket s, void *data, size_t *sizep, int flags);
+int nng_recvmsg(nng_socket s, nng_msg **msgp, int flags);
+void nng_recv_aio(nng_socket s, nng_aio *aio);
+```
+
+These functions ({{i:`nng_recv`}}, {{i:`nng_recvmsg`}}, and {{i:`nng_recv_aio`}}) receive
+messages over the socket _s_. The differences in their behaviors are as follows.
+
+> [!NOTE]
+> The semantics of what receving a message means varies from protocol to
+> protocol, so examination of the protocol documentation is encouraged.
+> Additionally, some protocols may not support receiving at all or may require other pre-conditions first.
+> (For example, [REQ][req] sockets cannot normally receive data until they have first sent a request,
+> while [PUB][pub] sockets can only send data and never receive it.)
+
+### nng_recv
+
+The `nng_recv` function is the simplest to use, but is the least efficient.
+It receives the content in _data_, as a message size (in bytes) of up to the value stored in _sizep_,
+unless the `NNG_FLAG_ALLOC` flag is set in _flags_ (see below.)
+
+Upon success, the size of the message received will be stored in _sizep_.
+
+The _flags_ is a bit mask made up of zero or more of the following values:
+
+- {{i:`NNG_FLAG_NONBLOCK`}}:
+  If the socket has no messages pending for reception at this time, it does not block, but returns immediately
+  with a status of [`NNG_EAGAIN`]. If this flag is absent, the function will wait until data can be received.
+
+- {{i:`NNG_FLAG_ALLOC`}}:
+  Instead of receiving the message into _data_, a new buffer will be allocated exactly large enough to hold
+  the message. A pointer to that buffer will be stored at the location specified by _data_. This provides a form
+  of zero-copy operation. The caller should dispose of the buffer using [`nng_free`] or by sending using
+  [`nng_send`] with the [`NNG_FLAG_ALLOC`] flag.
+
+> [!IMPORTANT]
+> When using `NNG_FLAG_ALLOC`, it is important that the value of _size_ match the actual allocated size of the data.
+> Using an incorrect size results in unspecified behavior, which may include heap corruption, program crashes,
+> or other undesirable effects.
+
+### nng_recvmsg
+
+The `nng_recvmsg` function receives a message and stores a pointer to the [`nng_msg`] for that message in _msgp_.
+
+The _flags_ can contain the value [`NNG_FLAG_NONBLOCK`], indicating that the function should not wait if the socket
+has no messages available to receive. In such a case, it will return [`NNG_EAGAIN`].
+
+> [!TIP]
+> This function is preferred over [`nng_recv`], as it gives access to the message structure and eliminates both
+> a data copy and allocation, even when `nng_recv` is using `NNG_FLAG_ALLOC`.
+
+### nng_recv_aio
+
+The `nng_send_aio` function receives a message asynchronously, using the [`nng_aio`] _aio_, over the socket _s_.
+On success, the received message can be retrieved from the _aio_ using the [`nng_aio_get_msg`] function.
+
+> [!NOTE]
+> It is important that the application retrieves the message, and disposes of it accordingly.
+> Failure to do so will leak the memory.
+
+> [!TIP]
+> This is the preferred function to use for receiving data on a socket. While it does require a few extra
+> steps on the part of the application, the lowest latencies and highest performance will be achieved by using
+> this function instead of [`nng_recv`] or [`nng_recvmsg`].
+
 ## Polling Socket Events
 
 ```c