fixes #143 Protocols and transports should be "configurable"

This makes all the protocols and transports optional.  All
of them except ZeroTier are enabled by default, but you can
now disable them (remove from the build) with cmake options.

The test suite is modified so that tests still run as much
as they can, but skip over things caused by missing functionality
from the library (due to configuration).

Further, the constant definitions and prototypes for functions
that are specific to transports or protocols are moved into
appropriate headers, which should be included directly by
applications wishing to use these.

We have also added and improved documentation -- all of the
transports are documented, and several more man pages for
protocols have been added.  (Req/Rep and Surveyor are still
missing.)

9 files changed, 597 insertions, 18 deletions

diff --git a/docs/nng_bus.adoc b/docs/nng_bus.adoc
index 03c43381..dd83062b 100644
--- a/docs/nng_bus.adoc
+++ b/docs/nng_bus.adoc
@@ -21,11 +21,9 @@ SYNOPSIS
 
 [source,c]
 ----------
-#include <nng/protocol/bus/bus.h>
+#include <nng/protocol/bus0/bus.h>
 
-int nng_bus_open(nng_socket *s);
 int nng_bus0_open(nng_socket *s);
-
 ----------
 
 DESCRIPTION
@@ -57,7 +55,7 @@ likely that message loss is to occur.
 Socket Operations
 ~~~~~~~~~~~~~~~~~
 
-The `nng_bus_open()` call creates a bus socket.  This socket
+The `nng_bus0_open()` call creates a bus socket.  This socket
 may be used to send and receive messages. Sending messages will
 attempt to deliver to each directly connected peer.
 
diff --git a/docs/nng_inproc.adoc b/docs/nng_inproc.adoc
index 9e044f6d..a6d83c95 100644
--- a/docs/nng_inproc.adoc
+++ b/docs/nng_inproc.adoc
@@ -47,8 +47,7 @@ URI Format
 
 This transport uses URIs using the scheme `inproc://`, followed by
 an arbitrary string of text, terminated by a `NUL` byte.  The
-entire URI must be less than `NNG_MAXADDRLEN` bytes long, including
-the terminating `NUL`.
+entire URI must be less than `NNG_MAXADDRLEN` bytes long.
 
 Multiple URIs can be used within the
 same application, and they will not interfere with one another.
@@ -65,16 +64,22 @@ When using an `nng_sockaddr` structure, the actual structure is of type
 
 [source,c]
 --------
-#define NNG_AF_INPROC 1
+#define NNG_AF_INPROC 1 <1>
 #define NNG_MAXADDRLEN 128
 
-struct nng_sockaddr_inproc {
+typedef nng_sockaddr_inproc {
+    // <2>
     uint16_t sa_family;                  // must be NNG_AF_INPROC
-    uint32_t sa_path[NNG_MAXADDRLEN];    // arbitrary "path"
+    char     sa_path[NNG_MAXADDRLEN];    // arbitrary "path"
+    //
 }
 --------
+<1> The values of these macros may change, so applications
+should avoid depending upon their values and instead use them symbolically.
+<2> Other members may be present, but only those listed here
+are suitable for application use.
 
-The `sa_family` member will have the value `NNG_AF_INPROC` (1).
+The `sa_family` member will have the value `NNG_AF_INPROC`.
 The `sa_path` member is an ASCIIZ string, and may contain any characters,
 terminated by a `NUL` byte.
 
diff --git a/docs/nng_ipc.adoc b/docs/nng_ipc.adoc
new file mode 100644
index 00000000..c5dac4f7
--- /dev/null
+++ b/docs/nng_ipc.adoc
@@ -0,0 +1,110 @@
+nng_ipc(7)
+==========
+:doctype: manpage
+:manmanual: nng
+:mansource: nng
+:icons: font
+:source-highlighter: pygments
+:copyright: Copyright 2017 Garrett D'Amore <garrett@damore.org> \
+            Copyright 2017 Capitar IT Group BV <info@capitar.com> \
+            This software 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_ipc - IPC transport for nng
+
+SYNOPSIS
+--------
+
+[source,c]
+----------
+#include <nng/transport/ipc/ipc.h>
+
+int nng_ipc_register(void);
+----------
+
+DESCRIPTION
+-----------
+
+The _nng_ipc_ transport provides communication support between
+_nng_ sockets within different processes on the same host. For POSIX
+platforms, this is implemented using UNIX domain sockets.  For Windows,
+this is implemented using Windows Named Pipes.  Other platforms may
+have different implementation strategies.
+
+// We need to insert a reference to the nanomsg RFC.
+
+Registration
+~~~~~~~~~~~~
+
+The _ipc_ transport is generally built-in to the _nng_ core, so
+no extra steps to use it should be necessary.
+
+URI Format
+~~~~~~~~~~
+
+This transport uses URIs using the scheme `ipc://`, followed by
+a path name in the file system where the socket or named pipe
+should be created.
+
+TIP: On Windows, all names are prefixed by `\.\pipe\` and do not
+occupy the normal file system.  On POSIX platforms, the path is
+taken literally, and is relative to the current directory, unless
+an extra leading `/` is provided.  For example, `ipc://myname` refers
+to the name `myname` in the current directory, whereas `ipc:///tmp/myname`
+refers to `myname` located in `/tmp`.
+
+The entire URI must be less than `NNG_MAXADDRLEN` bytes long.
+
+Socket Address
+~~~~~~~~~~~~~~
+
+When using an `nng_sockaddr` structure, the actual structure is of type
+`nng_sockaddr_ipc`.  This is a `struct` type with the following definition:
+
+[source,c]
+--------
+#define NNG_AF_IPC 2 <1>
+#define NNG_MAXADDRLEN 128
+
+typedef struct {
+    // ... <2>
+    uint16_t sa_family;                 // must be NNG_AF_IPC
+    char     sa_path[NNG_MAXADDRLEN];   // arbitrary "path"
+    // ...
+} nng_sockaddr_ipc;
+--------
+<1> The values of these macros may change, so applications
+should avoid depending upon their values and instead use them symbolically.
+<2> Other members may be present, but only those listed here
+are suitable for application use.
+
+The `sa_family` member will have the value `NNG_AF_IPC`.
+The `sa_path` member is an ASCIIZ string, and may contain any legal
+path name (platform-dependent), terminated by a `NUL` byte.
+
+Transport Options
+~~~~~~~~~~~~~~~~~
+
+The _ipc_ transport has no special
+options.footnote:[Options for security attributes and credentials are planned.]
+
+AUTHORS
+-------
+link:mailto:garrett@damore.org[Garrett D'Amore]
+
+SEE ALSO
+--------
+<<nng.adoc#,nng(7)>>
+
+COPYRIGHT
+---------
+
+Copyright 2017 mailto:garrett@damore.org[Garrett D'Amore] +
+Copyright 2017 mailto:info@capitar.com[Capitar IT Group BV]
+
+This document is supplied under the terms of the
+https://opensource.org/licenses/LICENSE.txt[MIT License].
diff --git a/docs/nng_pair.adoc b/docs/nng_pair.adoc
new file mode 100644
index 00000000..b55000af
--- /dev/null
+++ b/docs/nng_pair.adoc
@@ -0,0 +1,155 @@
+nng_pair(7)
+===========
+:doctype: manpage
+:manmanual: nng
+:mansource: nng
+:icons: font
+:source-highlighter: pygments
+:copyright: Copyright 2017 Garrett D'Amore <garrett@damore.org> \
+            Copyright 2017 Capitar IT Group BV <info@capitar.com> \
+            This software 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_pair - pair protocol
+
+SYNOPSIS
+--------
+
+.Version 0
+[source,c]
+----------
+#include <nng/protocol/pair0/pair.h>
+
+int nng_pair0_open(nng_socket *s);
+----------
+
+.Version 1
+[source,c]
+----------
+#include <nng/protocol/pair1/pair.h>
+
+int nng_pair1_open(nng_socket *s);
+----------
+
+DESCRIPTION
+-----------
+
+The _nng_pair_ protocol implements a peer-to-peer pattern, where
+relationships between peers are one-to-one.
+
+Version 1 of this protocol supports an optional _polyamorous_ mode where a
+peer can maintain multiple partnerships.  Using this mode requires
+some additional sophistication in the application.
+
+Socket Operations
+~~~~~~~~~~~~~~~~~
+
+The `nng_pair_open()` call creates a _pair_ socket.  Normally, this
+pattern will block when attempting to send a message, if no peer is
+able to receive the message.
+
+NOTE: Even though this mode may appear to be "reliable", because back-pressure
+prevents discarding messages most of the time, there are topologies involving
+_devices_ (see <<nng_device.adoc#,nng_device(3)>>) or raw mode sockets where
+messages may be discarded.  Applications that require reliable delivery
+semantics should consider using <<nng_req.adoc#,nng_req(7)>> sockets, or
+implement their own acknowledgement layer on top of pair sockets.
+
+In order to avoid head-of-line blocking conditions, _polyamorous_ mode pair
+sockets (version 1 only) discard messages if they are unable to deliver them
+to a peer.
+
+Protocol Versions
+~~~~~~~~~~~~~~~~~
+
+Version 0 is the legacy version of this protocol.  It lacks any header
+information, and is suitable when building simple one-to-one topologies.
+
+TIP: Use version 0 if you need to communicate with other implementations,
+including the legacy https://github.com/nanomsg/nanomsg[nanomsg] library or
+https://github.com/go-mangos/mangos[mangos].
+
+Version 1 of the protocol offers improved protection against loops when
+used with <<nng_device.adoc#,nng_device(3)>>.   It also offers _polyamorous_
+mode for forming multiple partnerships on a single socket.
+
+NOTE: Version 1 of this protocol is considered experimental at this time.
+
+Polyamorous Mode
+~~~~~~~~~~~~~~~~
+
+Normally pair sockets are for one-to-one communication, and a given peer
+will reject new connections if it already has an active connection to another
+peer.
+
+In _polyamorous_ mode, which is only available with version 1, a socket can
+support many one-to-one connections.  In this mode, the application must
+choose the remote peer to receive an ougoing message by setting the value
+of the pipe ID on the outgoing message using
+the <<nng_msg_set_pipe.adoc#,nng_msg_set_pipe(3)>> function.
+
+Most often the value of the outgoing pipe ID will be obtained from an incoming
+message using the <<nng_msg_get_pipe.adoc#,nng_msg_get_pipe(3)>> function,
+such as when replying to an incoming message.
+
+In order to prevent head-of-line blocking, if the peer on the given pipe
+is not able to receive (or the pipe is no longer available, such as if the
+peer has disconnected), then the message will be discarded with no notification
+to the sender.
+
+Protocol Options
+~~~~~~~~~~~~~~~~
+
+The following protocol-specific options are available.
+
+`NNG_OPT_PAIR1_POLY`::
+
+   (Version 1 only).  This option enables the use of _polyamorous_ mode.
+   The value is read-write, and takes an integer boolean value.  The default
+   false value (0) indicates that legacy monogamous mode should be used.
+
+`NNG_OPT_MAXTTL`::
+
+   (Version 1 only).  Maximum time-to-live.  This option is an integer value
+   between 0 and 255,
+   inclusive, and is the maximum number of "hops" that a message may
+   pass through until it is discarded.  The default value is 8.  A value
+   of 0 may be used to disable the loop protection, allowing an infinite
+   number of hops.
++
+TIP: Each node along a forwarding path may have it's own value for the
+maximum time-to-live, and performs its own checks before forwarding a message.
+Therefore it is helpful if all nodes in the topology use the same value for
+this option.
+
+Protocol Headers
+~~~~~~~~~~~~~~~~
+
+Version 0 of the pair protocol has no protocol-specific headers.
+
+Version 1 of the pair protocol uses a single 32-bit unsigned value.  The
+low-order (big-endian) byte of this value contains a "hop" count, and is
+used in conjuction with the `NNG_OPT_MAXTTL` option to guard against
+device forwarding loops.  This value is initialized to 1, and incremented
+each time the message is received by a new node.
+    
+AUTHORS
+-------
+link:mailto:garrett@damore.org[Garrett D'Amore]
+
+SEE ALSO
+--------
+<<nng.adoc#,nng(7)>>
+
+COPYRIGHT
+---------
+
+Copyright 2017 mailto:garrett@damore.org[Garrett D'Amore] +
+Copyright 2017 mailto:info@capitar.com[Capitar IT Group BV]
+
+This document is supplied under the terms of the
+https://opensource.org/licenses/LICENSE.txt[MIT License].
diff --git a/docs/nng_pub.adoc b/docs/nng_pub.adoc
index d4db45ae..4c3b764b 100644
--- a/docs/nng_pub.adoc
+++ b/docs/nng_pub.adoc
@@ -21,11 +21,9 @@ SYNOPSIS
 
 [source,c]
 ----------
-#include <nng/protocol/pubsub/pubsub.h>
+#include <nng/protocol/pubsub0/pub.h>
 
-int nng_pub_open(nng_socket *s);
 int nng_pub0_open(nng_socket *s);
-
 ----------
 
 DESCRIPTION
@@ -51,7 +49,7 @@ accordingly.
 Socket Operations
 ~~~~~~~~~~~~~~~~~
 
-The `nng_pub_open()` call creates a publisher socket.  This socket
+The `nng_pub0_open()` call creates a publisher socket.  This socket
 may be used to send messages, but is unable to receive them.  Attempts
 to receive messages will result in `NNG_ENOTSUP`.
 
diff --git a/docs/nng_pull.adoc b/docs/nng_pull.adoc
new file mode 100644
index 00000000..17614a3d
--- /dev/null
+++ b/docs/nng_pull.adoc
@@ -0,0 +1,85 @@
+nng_pull(7)
+===========
+:doctype: manpage
+:manmanual: nng
+:mansource: nng
+:icons: font
+:source-highlighter: pygments
+:copyright: Copyright 2017 Garrett D'Amore <garrett@damore.org> \
+            Copyright 2017 Capitar IT Group BV <info@capitar.com> \
+            This software 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_pull - pull protocol
+
+SYNOPSIS
+--------
+
+[source,c]
+----------
+#include <nng/protocol/pipeline0/pull.h>
+
+int nng_pull0_open(nng_socket *s);
+----------
+
+DESCRIPTION
+-----------
+
+The _nng_pull_ protocol is one half of a pipeline pattern. The other half
+is the <<nng_push.adoc#,nng_push(7)>> protocol.
+
+In the pipeline pattern, pushers distribute messages to pullers. 
+Each message sent
+by a pusher will be sent to one of its peer pullers,
+chosen in a round-robin fashion
+from the set of connected peers available for receiving.
+This property makes this pattern useful in load-balancing scenarios.
+
+Socket Operations
+~~~~~~~~~~~~~~~~~
+
+The `nng_pull0_open()` call creates a puller socket.  This socket
+may be used to receive messages, but is unable to send them.  Attempts
+to send messages will result in `NNG_ENOTSUP`.
+
+When receiving messages, the _nng_pull_ protocol accepts messages as
+they arrive from peers.  If two peers both have a message ready, the
+order in which messages are handled is undefined.
+
+Protocol Versions
+~~~~~~~~~~~~~~~~~
+
+Only version 0 of this protocol is supported.  (At the time of writing,
+no other versions of this protocol have been defined.)
+
+Protocol Options
+~~~~~~~~~~~~~~~~
+
+The _nng_pull_ protocol has no protocol-specific options.
+
+Protocol Headers
+~~~~~~~~~~~~~~~~
+
+The _nng_pull_ protocol has no protocol-specific headers.
+    
+AUTHORS
+-------
+link:mailto:garrett@damore.org[Garrett D'Amore]
+
+SEE ALSO
+--------
+<<nng.adoc#,nng(7)>>
+<<nng_push.adoc#,nng_push(7)>>
+
+COPYRIGHT
+---------
+
+Copyright 2017 mailto:garrett@damore.org[Garrett D'Amore] +
+Copyright 2017 mailto:info@capitar.com[Capitar IT Group BV]
+
+This document is supplied under the terms of the
+https://opensource.org/licenses/LICENSE.txt[MIT License].
diff --git a/docs/nng_push.adoc b/docs/nng_push.adoc
new file mode 100644
index 00000000..faf783b6
--- /dev/null
+++ b/docs/nng_push.adoc
@@ -0,0 +1,93 @@
+nng_push(7)
+===========
+:doctype: manpage
+:manmanual: nng
+:mansource: nng
+:icons: font
+:source-highlighter: pygments
+:copyright: Copyright 2017 Garrett D'Amore <garrett@damore.org> \
+            Copyright 2017 Capitar IT Group BV <info@capitar.com> \
+            This software 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_push - push protocol
+
+SYNOPSIS
+--------
+
+[source,c]
+----------
+#include <nng/protocol/pipeline0/push.h>
+
+int nng_push0_open(nng_socket *s);
+----------
+
+DESCRIPTION
+-----------
+
+The _nng_push_ protocol is one half of a pipeline pattern.  The
+other side is the <<nng_pull.adoc#,nng_pull(7)>> protocol.
+
+In the pipeline pattern, pushers distribute messages to pullers. 
+Each message sent
+by a pusher will be sent to one of its peer pullers,
+chosen in a round-robin fashion
+from the set of connected peers available for receiving.
+This property makes this pattern useful in load-balancing scenarios.
+
+Socket Operations
+~~~~~~~~~~~~~~~~~
+
+The `nng_push0_open()` call creates a pusher socket.  This socket
+may be used to send messages, but is unable to receive them.  Attempts
+to receive messages will result in `NNG_ENOTSUP`.
+
+Send operations will observe flow control (back-pressure), so that
+only peers capable of accepting a message will be considered.  If no
+peer is available to receive a message, then the send operation will
+wait until one is available, or the operation times out.
+
+NOTE: Although the pipeline protocol honors flow control, and attempts
+to avoid dropping messages, no guarantee of delivery is made.  Furthermore,
+as there is no capability for message acknowledgement, applications that
+need reliable delivery are encouraged to consider the
+<<nng_req.adoc#,nng_req(7)>> protocol instead.
+
+Protocol Versions
+~~~~~~~~~~~~~~~~~
+
+Only version 0 of this protocol is supported.  (At the time of writing,
+no other versions of this protocol have been defined.)
+
+Protocol Options
+~~~~~~~~~~~~~~~~
+
+The _nng_push_ protocol has no protocol-specific options.
+
+Protocol Headers
+~~~~~~~~~~~~~~~~
+
+The _nng_push_ protocol has no protocol-specific headers.
+    
+AUTHORS
+-------
+link:mailto:garrett@damore.org[Garrett D'Amore]
+
+SEE ALSO
+--------
+<<nng.adoc#,nng(7)>>
+<<nng_pull.adoc#,nng_pull(7)>>
+<<nng_req.adoc#,nng_req(7)>>
+
+COPYRIGHT
+---------
+
+Copyright 2017 mailto:garrett@damore.org[Garrett D'Amore] +
+Copyright 2017 mailto:info@capitar.com[Capitar IT Group BV]
+
+This document is supplied under the terms of the
+https://opensource.org/licenses/LICENSE.txt[MIT License].
diff --git a/docs/nng_sub.adoc b/docs/nng_sub.adoc
index 0b409904..5359acec 100644
--- a/docs/nng_sub.adoc
+++ b/docs/nng_sub.adoc
@@ -21,11 +21,9 @@ SYNOPSIS
 
 [source,c]
 ----------
-#include <nng/protocol/pubsub/pubsub.h>
+#include <nng/protocol/pubsub0/sub.h>
 
-int nng_sub_open(nng_socket *s);
 int nng_sub0_open(nng_socket *s);
-
 ----------
 
 DESCRIPTION
@@ -51,7 +49,7 @@ accordingly.
 Socket Operations
 ~~~~~~~~~~~~~~~~~
 
-The `nng_sub_open()` call creates a subscriber socket.  This socket
+The `nng_sub0_open()` call creates a subscriber socket.  This socket
 may be used to receive messages, but is unable to send them.  Attempts
 to send messages will result in `NNG_ENOTSUP`.
 
diff --git a/docs/nng_tcp.adoc b/docs/nng_tcp.adoc
new file mode 100644
index 00000000..a1d0cdab
--- /dev/null
+++ b/docs/nng_tcp.adoc
@@ -0,0 +1,137 @@
+nng_tcp(7)
+==========
+:doctype: manpage
+:manmanual: nng
+:mansource: nng
+:icons: font
+:source-highlighter: pygments
+:copyright: Copyright 2017 Garrett D'Amore <garrett@damore.org> \
+            Copyright 2017 Capitar IT Group BV <info@capitar.com> \
+            This software 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_tcp - TCP/IP transport for nng
+
+SYNOPSIS
+--------
+
+[source,c]
+----------
+#include <nng/transport/tcp/tcp.h>
+
+int nng_tcp_register(void);
+----------
+
+DESCRIPTION
+-----------
+
+The _nng_tcp_ transport provides communication support between
+_nng_ sockets across a TCP/IP network.  Both IPv4 and IPv6
+are supported when the underlying platform also supports it.
+
+// We need to insert a reference to the nanomsg RFC.
+
+Registration
+~~~~~~~~~~~~
+
+The _tcp_ transport is generally built-in to the _nng_ core, so
+no extra steps to use it should be necessary.
+
+URI Format
+~~~~~~~~~~
+
+This transport uses URIs using the scheme `tcp://`, followed by
+an IP address or hostname, followed by a colon and finally a
+TCP port number.  For example, to contact port 80 on the localhost
+either of the following URIs could be used: `tcp://127.0.0.1:80` or
+`tcp://localhost:80`.
+
+When specifying IPv6 addresses, the address must be enclosed in
+square brackets (`[]`) to avoid confusion with the final colon
+separating the port.
+
+For example, the same port 80 on the IPv6 loopback address ('::1') would
+be specified as `tcp://[::1]:80`.
+
+NOTE: When using symbolic names, the name is resolved when the
+name is first used. _nng_ won't become aware of changes in the
+name resolution until restart,
+usually.footnote:[This is a bug and will likely be fixed in the future.]
+
+The special value of 0 (`INADDR_ANY`) can be used for a listener
+to indicate that it should listen on all interfaces on the host.
+A short-hand for this form is to either omit the address, or specify
+the asterisk (`*`) character.  For example, the following three
+URIs are all equivalent, and could be used to listen to port 9999
+on the host:
+
+  1. `tcp://0.0.0.0:9999`
+  2. `tcp://*:9999`
+  3. `tcp://:9999`
+
+The entire URI must be less than `NNG_MAXADDRLEN` bytes long.
+
+Socket Address
+~~~~~~~~~~~~~~
+
+When using an `nng_sockaddr` structure, the actual structure is either
+of type `nng_sockaddr_in` (for IPv4) or `nng_sockaddr_in6` (for IPv6).
+These are `struct` types with the following definitions:
+
+[source,c]
+--------
+#define NNG_AF_INET    3 <1>
+#define NNG_AF_INET6   4
+#define NNG_MAXADDRLEN 128
+
+typedef struct {
+    // ... <2>
+    uint16_t sa_family;                 // must be NNG_AF_INET
+    uint16_t sa_port;                   // TCP port number
+    uint32_t sa_addr;
+    // ...
+} nng_sockaddr_in;
+
+typedef struct {
+    // ... <2>
+    uint16_t sa_family;                 // must be NNG_AF_INET6
+    uint16_t sa_port;                   // TCP port number
+    uint8_t  sa_addr[16];
+    // ...
+} nng_sockaddr_in6;
+--------
+<1> The values of these macros may change, so applications
+should avoid depending upon their values and instead use them symbolically.
+<2> Other members may be present, but only those listed here
+are suitable for application use.
+
+The `sa_family` member will have the value `NNG_AF_INET` or `NNG_AF_INET6`.
+The `sa_port` and `sa_addr` are the TCP port number and address, both in
+network byte order (most significant byte is first).
+
+Transport Options
+~~~~~~~~~~~~~~~~~
+
+The _tcp_ transport has no special
+options.footnote:[Options for TCP keepalive, linger, and nodelay are planned.]
+ 
+AUTHORS
+-------
+link:mailto:garrett@damore.org[Garrett D'Amore]
+
+SEE ALSO
+--------
+<<nng.adoc#,nng(7)>>
+
+COPYRIGHT
+---------
+
+Copyright 2017 mailto:garrett@damore.org[Garrett D'Amore] +
+Copyright 2017 mailto:info@capitar.com[Capitar IT Group BV]
+
+This document is supplied under the terms of the
+https://opensource.org/licenses/LICENSE.txt[MIT License].