Add new PAIR_V1 protocol.

The PAIR_V1 protocol supports both raw and cooked modes, and has loop
prevention included.  It also has a polyamorous mode, wherein it allows
multiple connections to be established.  In polyamorous mode (set by
an option), the sender requests a paritcular pipe by setting it on the
message.

We default to PAIR_V1 now.

9 files changed, 914 insertions, 344 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index ad6c025e..9ecce72c 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -108,7 +108,8 @@ set (NNG_SOURCES
 
     protocol/bus/bus.c
 
-    protocol/pair/pair.c
+    protocol/pair/pair_v0.c
+    protocol/pair/pair_v1.c
 
     protocol/pipeline/pull.c
     protocol/pipeline/push.c
diff --git a/src/core/message.c b/src/core/message.c
index 4b563ce2..316bc035 100644
--- a/src/core/message.c
+++ b/src/core/message.c
@@ -1,5 +1,6 @@
 //
 // Copyright 2016 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
@@ -29,6 +30,7 @@ struct nng_msg {
 	nni_chunk m_body;
 	nni_time  m_expire; // usec
 	nni_list  m_options;
+	uint32_t  m_pipe; // set on receive
 };
 
 typedef struct {
@@ -264,6 +266,42 @@ nni_chunk_prepend(nni_chunk *ch, const void *data, size_t len)
 	return (0);
 }
 
+static int
+nni_chunk_prepend_u32(nni_chunk *ch, uint32_t val)
+{
+	unsigned char buf[sizeof(uint32_t)];
+	NNI_PUT32(buf, val);
+	return (nni_chunk_prepend(ch, buf, sizeof(buf)));
+}
+
+static int
+nni_chunk_append_u32(nni_chunk *ch, uint32_t val)
+{
+	unsigned char buf[sizeof(uint32_t)];
+	NNI_PUT32(buf, val);
+	return (nni_chunk_append(ch, buf, sizeof(buf)));
+}
+
+static uint32_t
+nni_chunk_trim_u32(nni_chunk *ch)
+{
+	uint32_t v;
+	NNI_ASSERT(ch->ch_len >= sizeof(v));
+	NNI_GET32(ch->ch_ptr, v);
+	nni_chunk_trim(ch, sizeof(v));
+	return (v);
+}
+
+static uint32_t
+nni_chunk_trunc_u32(nni_chunk *ch)
+{
+	uint32_t v;
+	NNI_ASSERT(ch->ch_len >= sizeof(v));
+	NNI_GET32(ch->ch_ptr + ch->ch_len - sizeof(v), v);
+	nni_chunk_trunc(ch, sizeof(v));
+	return (v);
+}
+
 int
 nni_msg_alloc(nni_msg **mp, size_t sz)
 {
@@ -483,7 +521,6 @@ nni_msg_append_header(nni_msg *m, const void *data, size_t len)
 {
 	return (nni_chunk_append(&m->m_header, data, len));
 }
-
 int
 nni_msg_prepend_header(nni_msg *m, const void *data, size_t len)
 {
@@ -501,3 +538,61 @@ nni_msg_trunc_header(nni_msg *m, size_t len)
 {
 	return (nni_chunk_trunc(&m->m_header, len));
 }
+int
+nni_msg_append_u32(nni_msg *m, uint32_t val)
+{
+	return (nni_chunk_append_u32(&m->m_body, val));
+}
+
+int
+nni_msg_prepend_u32(nni_msg *m, uint32_t val)
+{
+	return (nni_chunk_prepend_u32(&m->m_body, val));
+}
+
+int
+nni_msg_header_append_u32(nni_msg *m, uint32_t val)
+{
+	return (nni_chunk_append_u32(&m->m_header, val));
+}
+
+int
+nni_msg_header_prepend_u32(nni_msg *m, uint32_t val)
+{
+	return (nni_chunk_prepend_u32(&m->m_header, val));
+}
+
+uint32_t
+nni_msg_trunc_u32(nni_msg *m)
+{
+	return (nni_chunk_trunc_u32(&m->m_body));
+}
+
+uint32_t
+nni_msg_trim_u32(nni_msg *m)
+{
+	return (nni_chunk_trim_u32(&m->m_body));
+}
+
+uint32_t
+nni_msg_header_trunc_u32(nni_msg *m)
+{
+	return (nni_chunk_trunc_u32(&m->m_header));
+}
+uint32_t
+nni_msg_header_trim_u32(nni_msg *m)
+{
+	return (nni_chunk_trim_u32(&m->m_header));
+}
+
+void
+nni_msg_set_pipe(nni_msg *m, uint32_t pid)
+{
+	m->m_pipe = pid;
+}
+
+uint32_t
+nni_msg_get_pipe(nni_msg *m)
+{
+	return (m->m_pipe);
+}
\ No newline at end of file
diff --git a/src/core/message.h b/src/core/message.h
index 7b71bd5c..4bc15321 100644
--- a/src/core/message.h
+++ b/src/core/message.h
@@ -1,5 +1,6 @@
 //
-// Copyright 2016 Garrett D'Amore <garrett@damore.org>
+// 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
@@ -12,24 +13,34 @@
 
 // Internally used message API.  Again, this is not part of our public API.
 
-extern int    nni_msg_alloc(nni_msg **, size_t);
-extern void   nni_msg_free(nni_msg *);
-extern int    nni_msg_realloc(nni_msg *, size_t);
-extern int    nni_msg_dup(nni_msg **, const nni_msg *);
-extern void * nni_msg_header(nni_msg *);
-extern size_t nni_msg_header_len(nni_msg *);
-extern void * nni_msg_body(nni_msg *);
-extern size_t nni_msg_len(nni_msg *);
-extern int    nni_msg_append(nni_msg *, const void *, size_t);
-extern int    nni_msg_prepend(nni_msg *, const void *, size_t);
-extern int    nni_msg_append_header(nni_msg *, const void *, size_t);
-extern int    nni_msg_prepend_header(nni_msg *, const void *, size_t);
-extern int    nni_msg_trim(nni_msg *, size_t);
-extern int    nni_msg_trunc(nni_msg *, size_t);
-extern int    nni_msg_trim_header(nni_msg *, size_t);
-extern int    nni_msg_trunc_header(nni_msg *, size_t);
-extern int    nni_msg_setopt(nni_msg *, int, const void *, size_t);
-extern int    nni_msg_getopt(nni_msg *, int, void *, size_t *);
-extern void   nni_msg_dump(const char *, const nni_msg *);
+extern int      nni_msg_alloc(nni_msg **, size_t);
+extern void     nni_msg_free(nni_msg *);
+extern int      nni_msg_realloc(nni_msg *, size_t);
+extern int      nni_msg_dup(nni_msg **, const nni_msg *);
+extern void *   nni_msg_header(nni_msg *);
+extern size_t   nni_msg_header_len(nni_msg *);
+extern void *   nni_msg_body(nni_msg *);
+extern size_t   nni_msg_len(nni_msg *);
+extern int      nni_msg_append(nni_msg *, const void *, size_t);
+extern int      nni_msg_prepend(nni_msg *, const void *, size_t);
+extern int      nni_msg_append_header(nni_msg *, const void *, size_t);
+extern int      nni_msg_prepend_header(nni_msg *, const void *, size_t);
+extern int      nni_msg_trim(nni_msg *, size_t);
+extern int      nni_msg_trunc(nni_msg *, size_t);
+extern int      nni_msg_trim_header(nni_msg *, size_t);
+extern int      nni_msg_trunc_header(nni_msg *, size_t);
+extern int      nni_msg_setopt(nni_msg *, int, const void *, size_t);
+extern int      nni_msg_getopt(nni_msg *, int, void *, size_t *);
+extern void     nni_msg_dump(const char *, const nni_msg *);
+extern int      nni_msg_append_u32(nni_msg *, uint32_t);
+extern int      nni_msg_prepend_u32(nni_msg *, uint32_t);
+extern int      nni_msg_header_append_u32(nni_msg *, uint32_t);
+extern int      nni_msg_header_prepend_u32(nni_msg *, uint32_t);
+extern uint32_t nni_msg_trim_u32(nni_msg *);
+extern uint32_t nni_msg_trunc_u32(nni_msg *);
+extern uint32_t nni_msg_header_trim_u32(nni_msg *);
+extern uint32_t nni_msg_header_trunc_u32(nni_msg *);
+extern void     nni_msg_set_pipe(nni_msg *, uint32_t);
+extern uint32_t nni_msg_get_pipe(nni_msg *);
 
 #endif // CORE_SOCKET_H
diff --git a/src/nng.h b/src/nng.h
index 99c95b92..247be1f7 100644
--- a/src/nng.h
+++ b/src/nng.h
@@ -1,5 +1,6 @@
 //
 // 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
@@ -290,6 +291,7 @@ enum nng_flag_enum {
 enum nng_proto_enum {
 	NNG_PROTO_NONE          = NNG_PROTO(0, 0),
 	NNG_PROTO_PAIR_V0       = NNG_PROTO(1, 0),
+	NNG_PROTO_PAIR_V1       = NNG_PROTO(1, 1),
 	NNG_PROTO_PUB_V0        = NNG_PROTO(2, 0),
 	NNG_PROTO_SUB_V0        = NNG_PROTO(2, 1),
 	NNG_PROTO_REQ_V0        = NNG_PROTO(3, 0),
@@ -301,9 +303,10 @@ enum nng_proto_enum {
 	NNG_PROTO_BUS_V0        = NNG_PROTO(7, 0),
 	NNG_PROTO_STAR_V0       = NNG_PROTO(100, 0),
 
-	// "Legacy" names.  Please use explicit versioned names above.
+	// "Default" names.  Use the explicit version to guarantee
+	// backwards compatibility.
 	NNG_PROTO_BUS        = NNG_PROTO_BUS_V0,
-	NNG_PROTO_PAIR       = NNG_PROTO_PAIR_V0,
+	NNG_PROTO_PAIR       = NNG_PROTO_PAIR_V1,
 	NNG_PROTO_SUB        = NNG_PROTO_SUB_V0,
 	NNG_PROTO_PUB        = NNG_PROTO_PUB_V0,
 	NNG_PROTO_REQ        = NNG_PROTO_REQ_V0,
@@ -317,6 +320,7 @@ enum nng_proto_enum {
 // Builtin protocol socket constructors.
 extern int nng_bus0_open(nng_socket *);
 extern int nng_pair0_open(nng_socket *);
+extern int nng_pair1_open(nng_socket *);
 extern int nng_pub0_open(nng_socket *);
 extern int nng_sub0_open(nng_socket *);
 extern int nng_push0_open(nng_socket *);
@@ -330,7 +334,7 @@ extern int nng_respondent0_open(nng_socket *);
 // the actual protocols are baked into the binary; this should avoid
 // suprising.  Choosing a new protocol should be done explicitly.
 #define nng_bus_open nng_bus0_open
-#define nng_pair_open nng_pair0_open
+#define nng_pair_open nng_pair1_open
 #define nng_pub_open nng_pub0_open
 #define nng_sub_open nng_sub0_open
 #define nng_push_open nng_push0_open
@@ -369,6 +373,7 @@ enum nng_opt_enum {
 	NNG_OPT_REMOTEADDR     = NNG_OPT_SOCKET(17),
 	NNG_OPT_RCVFD          = NNG_OPT_SOCKET(18),
 	NNG_OPT_SNDFD          = NNG_OPT_SOCKET(19),
+	NNG_OPT_POLYAMOROUS    = NNG_OPT_SOCKET(20),
 };
 
 // XXX: TBD: priorities, socket names, ipv4only
diff --git a/src/nng_compat.c b/src/nng_compat.c
index e03ff42d..dfcb2134 100644
--- a/src/nng_compat.c
+++ b/src/nng_compat.c
@@ -92,19 +92,18 @@ static const struct {
 	uint16_t p_id;
 	int (*p_open)(nng_socket *);
 } nn_protocols[] = {
-	// clang-format off
-	{ NNG_PROTO_BUS_V0, nng_bus_open },
-	{ NNG_PROTO_PAIR_V0, nng_pair_open },
-	{ NNG_PROTO_PUSH_V0, nng_push_open },
-	{ NNG_PROTO_PULL_V0, nng_pull_open },
-	{ NNG_PROTO_PUB_V0, nng_pub_open },
-	{ NNG_PROTO_SUB_V0, nng_sub_open },
-	{ NNG_PROTO_REQ_V0, nng_req_open },
-	{ NNG_PROTO_REP_V0, nng_rep_open },
-	{ NNG_PROTO_SURVEYOR_V0, nng_surveyor_open },
-	{ NNG_PROTO_RESPONDENT_V0, nng_respondent_open },
+	{ NNG_PROTO_BUS_V0, nng_bus0_open },
+	{ NNG_PROTO_PAIR_V0, nng_pair0_open },
+	{ NNG_PROTO_PAIR_V0, nng_pair1_open },
+	{ NNG_PROTO_PUSH_V0, nng_push0_open },
+	{ NNG_PROTO_PULL_V0, nng_pull0_open },
+	{ NNG_PROTO_PUB_V0, nng_pub0_open },
+	{ NNG_PROTO_SUB_V0, nng_sub0_open },
+	{ NNG_PROTO_REQ_V0, nng_req0_open },
+	{ NNG_PROTO_REP_V0, nng_rep0_open },
+	{ NNG_PROTO_SURVEYOR_V0, nng_surveyor0_open },
+	{ NNG_PROTO_RESPONDENT_V0, nng_respondent0_open },
 	{ NNG_PROTO_NONE, NULL },
-	// clang-format on
 };
 
 int
diff --git a/src/nng_compat.h b/src/nng_compat.h
index e83c20b8..76494b5c 100644
--- a/src/nng_compat.h
+++ b/src/nng_compat.h
@@ -72,6 +72,8 @@ extern "C" {
 #define NN_PROTO_BUS		7
 
 #define NN_PAIR			(NN_PROTO_PAIR * 16 + 0)
+#define NN_PAIR_v0		(NN_PROTO_PAIR * 16 + 0)
+#define NN_PAIR_V1		(NN_PROTO_PAIR * 16 + 1)
 #define NN_PUB			(NN_PROTO_PUBSUB * 16 + 0)
 #define NN_SUB			(NN_PROTO_PUBSUB * 16 + 1)
 #define NN_REQ			(NN_PROTO_REQREP * 16 + 0)
diff --git a/src/protocol/pair/pair.c b/src/protocol/pair/pair.c
deleted file mode 100644
index 59465293..00000000
--- a/src/protocol/pair/pair.c
+++ /dev/null
@@ -1,307 +0,0 @@
-//
-// 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.
-//
-
-#include <stdlib.h>
-#include <string.h>
-
-#include "core/nng_impl.h"
-
-// Pair protocol.  The PAIR protocol is a simple 1:1 messaging pattern.
-// While a peer is connected to the server, all other peer connection
-// attempts are discarded.
-
-typedef struct nni_pair_pipe nni_pair_pipe;
-typedef struct nni_pair_sock nni_pair_sock;
-
-static void nni_pair_send_cb(void *);
-static void nni_pair_recv_cb(void *);
-static void nni_pair_getq_cb(void *);
-static void nni_pair_putq_cb(void *);
-static void nni_pair_pipe_fini(void *);
-
-// An nni_pair_sock is our per-socket protocol private structure.
-struct nni_pair_sock {
-	nni_sock *     nsock;
-	nni_pair_pipe *ppipe;
-	nni_msgq *     uwq;
-	nni_msgq *     urq;
-	int            raw;
-	nni_mtx        mtx;
-};
-
-// An nni_pair_pipe is our per-pipe protocol private structure.  We keep
-// one of these even though in theory we'd only have a single underlying
-// pipe.  The separate data structure is more like other protocols that do
-// manage multiple pipes.
-struct nni_pair_pipe {
-	nni_pipe *     npipe;
-	nni_pair_sock *psock;
-	nni_aio        aio_send;
-	nni_aio        aio_recv;
-	nni_aio        aio_getq;
-	nni_aio        aio_putq;
-};
-
-static int
-nni_pair_sock_init(void **sp, nni_sock *nsock)
-{
-	nni_pair_sock *psock;
-	int            rv;
-
-	if ((psock = NNI_ALLOC_STRUCT(psock)) == NULL) {
-		return (NNG_ENOMEM);
-	}
-	if ((rv = nni_mtx_init(&psock->mtx)) != 0) {
-		NNI_FREE_STRUCT(psock);
-		return (rv);
-	}
-	psock->nsock = nsock;
-	psock->ppipe = NULL;
-	psock->raw   = 0;
-	psock->uwq   = nni_sock_sendq(nsock);
-	psock->urq   = nni_sock_recvq(nsock);
-	*sp          = psock;
-	return (0);
-}
-
-static void
-nni_pair_sock_fini(void *arg)
-{
-	nni_pair_sock *psock = arg;
-
-	if (psock != NULL) {
-		nni_mtx_fini(&psock->mtx);
-
-		NNI_FREE_STRUCT(psock);
-	}
-}
-
-static int
-nni_pair_pipe_init(void **pp, nni_pipe *npipe, void *psock)
-{
-	nni_pair_pipe *ppipe;
-	int            rv;
-
-	if ((ppipe = NNI_ALLOC_STRUCT(ppipe)) == NULL) {
-		return (NNG_ENOMEM);
-	}
-	rv = nni_aio_init(&ppipe->aio_send, nni_pair_send_cb, ppipe);
-	if (rv != 0) {
-		goto fail;
-	}
-	rv = nni_aio_init(&ppipe->aio_recv, nni_pair_recv_cb, ppipe);
-	if (rv != 0) {
-		goto fail;
-	}
-	rv = nni_aio_init(&ppipe->aio_getq, nni_pair_getq_cb, ppipe);
-	if (rv != 0) {
-		goto fail;
-	}
-	rv = nni_aio_init(&ppipe->aio_putq, nni_pair_putq_cb, ppipe);
-	if (rv != 0) {
-		goto fail;
-	}
-	ppipe->npipe = npipe;
-	ppipe->psock = psock;
-	*pp          = ppipe;
-	return (0);
-
-fail:
-	nni_pair_pipe_fini(ppipe);
-	return (rv);
-}
-
-static void
-nni_pair_pipe_fini(void *arg)
-{
-	nni_pair_pipe *ppipe = arg;
-	nni_aio_fini(&ppipe->aio_send);
-	nni_aio_fini(&ppipe->aio_recv);
-	nni_aio_fini(&ppipe->aio_putq);
-	nni_aio_fini(&ppipe->aio_getq);
-	NNI_FREE_STRUCT(ppipe);
-}
-
-static int
-nni_pair_pipe_start(void *arg)
-{
-	nni_pair_pipe *ppipe = arg;
-	nni_pair_sock *psock = ppipe->psock;
-
-	nni_mtx_lock(&psock->mtx);
-	if (psock->ppipe != NULL) {
-		nni_mtx_unlock(&psock->mtx);
-		return (NNG_EBUSY); // Already have a peer, denied.
-	}
-	psock->ppipe = ppipe;
-	nni_mtx_unlock(&psock->mtx);
-
-	// Schedule a getq on the upper, and a read from the pipe.
-	// Each of these also sets up another hold on the pipe itself.
-	nni_msgq_aio_get(psock->uwq, &ppipe->aio_getq);
-	nni_pipe_recv(ppipe->npipe, &ppipe->aio_recv);
-
-	return (0);
-}
-
-static void
-nni_pair_pipe_stop(void *arg)
-{
-	nni_pair_pipe *ppipe = arg;
-	nni_pair_sock *psock = ppipe->psock;
-
-	nni_aio_cancel(&ppipe->aio_send, NNG_ECANCELED);
-	nni_aio_cancel(&ppipe->aio_recv, NNG_ECANCELED);
-	nni_aio_cancel(&ppipe->aio_putq, NNG_ECANCELED);
-	nni_aio_cancel(&ppipe->aio_getq, NNG_ECANCELED);
-
-	nni_mtx_lock(&psock->mtx);
-	if (psock->ppipe == ppipe) {
-		psock->ppipe = NULL;
-	}
-	nni_mtx_unlock(&psock->mtx);
-}
-
-static void
-nni_pair_recv_cb(void *arg)
-{
-	nni_pair_pipe *ppipe = arg;
-	nni_pair_sock *psock = ppipe->psock;
-
-	if (nni_aio_result(&ppipe->aio_recv) != 0) {
-		nni_pipe_stop(ppipe->npipe);
-		return;
-	}
-
-	ppipe->aio_putq.a_msg = ppipe->aio_recv.a_msg;
-	ppipe->aio_recv.a_msg = NULL;
-	nni_msgq_aio_put(psock->urq, &ppipe->aio_putq);
-}
-
-static void
-nni_pair_putq_cb(void *arg)
-{
-	nni_pair_pipe *ppipe = arg;
-
-	if (nni_aio_result(&ppipe->aio_putq) != 0) {
-		nni_msg_free(ppipe->aio_putq.a_msg);
-		ppipe->aio_putq.a_msg = NULL;
-		nni_pipe_stop(ppipe->npipe);
-		return;
-	}
-	nni_pipe_recv(ppipe->npipe, &ppipe->aio_recv);
-}
-
-static void
-nni_pair_getq_cb(void *arg)
-{
-	nni_pair_pipe *ppipe = arg;
-	nni_pair_sock *psock = ppipe->psock;
-
-	if (nni_aio_result(&ppipe->aio_getq) != 0) {
-		nni_pipe_stop(ppipe->npipe);
-		return;
-	}
-
-	ppipe->aio_send.a_msg = ppipe->aio_getq.a_msg;
-	ppipe->aio_getq.a_msg = NULL;
-	nni_pipe_send(ppipe->npipe, &ppipe->aio_send);
-}
-
-static void
-nni_pair_send_cb(void *arg)
-{
-	nni_pair_pipe *ppipe = arg;
-	nni_pair_sock *psock = ppipe->psock;
-
-	if (nni_aio_result(&ppipe->aio_send) != 0) {
-		nni_msg_free(ppipe->aio_send.a_msg);
-		ppipe->aio_send.a_msg = NULL;
-		nni_pipe_stop(ppipe->npipe);
-		return;
-	}
-
-	nni_msgq_aio_get(psock->uwq, &ppipe->aio_getq);
-}
-
-static void
-nni_pair_sock_open(void *arg)
-{
-	NNI_ARG_UNUSED(arg);
-}
-
-static void
-nni_pair_sock_close(void *arg)
-{
-	NNI_ARG_UNUSED(arg);
-}
-
-static int
-nni_pair_sock_setopt(void *arg, int opt, const void *buf, size_t sz)
-{
-	nni_pair_sock *psock = arg;
-	int            rv;
-
-	switch (opt) {
-	case NNG_OPT_RAW:
-		rv = nni_setopt_int(&psock->raw, buf, sz, 0, 1);
-		break;
-	default:
-		rv = NNG_ENOTSUP;
-	}
-	return (rv);
-}
-
-static int
-nni_pair_sock_getopt(void *arg, int opt, void *buf, size_t *szp)
-{
-	nni_pair_sock *psock = arg;
-	int            rv;
-
-	switch (opt) {
-	case NNG_OPT_RAW:
-		rv = nni_getopt_int(&psock->raw, buf, szp);
-		break;
-	default:
-		rv = NNG_ENOTSUP;
-	}
-	return (rv);
-}
-
-static nni_proto_pipe_ops nni_pair_pipe_ops = {
-	.pipe_init  = nni_pair_pipe_init,
-	.pipe_fini  = nni_pair_pipe_fini,
-	.pipe_start = nni_pair_pipe_start,
-	.pipe_stop  = nni_pair_pipe_stop,
-};
-
-static nni_proto_sock_ops nni_pair_sock_ops = {
-	.sock_init   = nni_pair_sock_init,
-	.sock_fini   = nni_pair_sock_fini,
-	.sock_open   = nni_pair_sock_open,
-	.sock_close  = nni_pair_sock_close,
-	.sock_setopt = nni_pair_sock_setopt,
-	.sock_getopt = nni_pair_sock_getopt,
-};
-
-nni_proto nni_pair_proto = {
-	.proto_version  = NNI_PROTOCOL_VERSION,
-	.proto_self     = { NNG_PROTO_PAIR_V0, "pair" },
-	.proto_peer     = { NNG_PROTO_PAIR_V0, "pair" },
-	.proto_flags    = NNI_PROTO_FLAG_SNDRCV,
-	.proto_sock_ops = &nni_pair_sock_ops,
-	.proto_pipe_ops = &nni_pair_pipe_ops,
-};
-
-int
-nng_pair0_open(nng_socket *sidp)
-{
-	return (nni_proto_open(sidp, &nni_pair_proto));
-}
diff --git a/src/protocol/pair/pair_v0.c b/src/protocol/pair/pair_v0.c
new file mode 100644
index 00000000..a0e907f2
--- /dev/null
+++ b/src/protocol/pair/pair_v0.c
@@ -0,0 +1,297 @@
+//
+// 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.
+//
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "core/nng_impl.h"
+
+// Pair protocol.  The PAIR protocol is a simple 1:1 messaging pattern.
+// While a peer is connected to the server, all other peer connection
+// attempts are discarded.
+
+typedef struct pair0_pipe pair0_pipe;
+typedef struct pair0_sock pair0_sock;
+
+static void pair0_send_cb(void *);
+static void pair0_recv_cb(void *);
+static void pair0_getq_cb(void *);
+static void pair0_putq_cb(void *);
+static void pair0_pipe_fini(void *);
+
+// pair0_sock is our per-socket protocol private structure.
+struct pair0_sock {
+	nni_sock *  nsock;
+	pair0_pipe *ppipe;
+	nni_msgq *  uwq;
+	nni_msgq *  urq;
+	int         raw;
+	nni_mtx     mtx;
+};
+
+// An pair0_pipe is our per-pipe protocol private structure.  We keep
+// one of these even though in theory we'd only have a single underlying
+// pipe.  The separate data structure is more like other protocols that do
+// manage multiple pipes.
+struct pair0_pipe {
+	nni_pipe *  npipe;
+	pair0_sock *psock;
+	nni_aio     aio_send;
+	nni_aio     aio_recv;
+	nni_aio     aio_getq;
+	nni_aio     aio_putq;
+};
+
+static int
+pair0_sock_init(void **sp, nni_sock *nsock)
+{
+	pair0_sock *s;
+	int         rv;
+
+	if ((s = NNI_ALLOC_STRUCT(s)) == NULL) {
+		return (NNG_ENOMEM);
+	}
+	if ((rv = nni_mtx_init(&s->mtx)) != 0) {
+		NNI_FREE_STRUCT(s);
+		return (rv);
+	}
+	s->nsock = nsock;
+	s->ppipe = NULL;
+	s->raw   = 0;
+	s->uwq   = nni_sock_sendq(nsock);
+	s->urq   = nni_sock_recvq(nsock);
+	*sp      = s;
+	return (0);
+}
+
+static void
+pair0_sock_fini(void *arg)
+{
+	pair0_sock *s = arg;
+
+	nni_mtx_fini(&s->mtx);
+	NNI_FREE_STRUCT(s);
+}
+
+static int
+pair0_pipe_init(void **pp, nni_pipe *npipe, void *psock)
+{
+	pair0_pipe *p;
+	int         rv;
+
+	if ((p = NNI_ALLOC_STRUCT(p)) == NULL) {
+		return (NNG_ENOMEM);
+	}
+	if (((rv = nni_aio_init(&p->aio_send, pair0_send_cb, p)) != 0) ||
+	    ((rv = nni_aio_init(&p->aio_recv, pair0_recv_cb, p)) != 0) ||
+	    ((rv = nni_aio_init(&p->aio_getq, pair0_getq_cb, p)) != 0) ||
+	    ((rv = nni_aio_init(&p->aio_putq, pair0_putq_cb, p)) != 0)) {
+		pair0_pipe_fini(p);
+	} else {
+		p->npipe = npipe;
+		p->psock = psock;
+		*pp      = p;
+	}
+	return (rv);
+}
+
+static void
+pair0_pipe_fini(void *arg)
+{
+	pair0_pipe *p = arg;
+
+	nni_aio_fini(&p->aio_send);
+	nni_aio_fini(&p->aio_recv);
+	nni_aio_fini(&p->aio_putq);
+	nni_aio_fini(&p->aio_getq);
+	NNI_FREE_STRUCT(p);
+}
+
+static int
+pair0_pipe_start(void *arg)
+{
+	pair0_pipe *p = arg;
+	pair0_sock *s = p->psock;
+
+	nni_mtx_lock(&s->mtx);
+	if (s->ppipe != NULL) {
+		nni_mtx_unlock(&s->mtx);
+		return (NNG_EBUSY); // Already have a peer, denied.
+	}
+	s->ppipe = p;
+	nni_mtx_unlock(&s->mtx);
+
+	// Schedule a getq on the upper, and a read from the pipe.
+	// Each of these also sets up another hold on the pipe itself.
+	nni_msgq_aio_get(s->uwq, &p->aio_getq);
+	nni_pipe_recv(p->npipe, &p->aio_recv);
+
+	return (0);
+}
+
+static void
+pair0_pipe_stop(void *arg)
+{
+	pair0_pipe *p = arg;
+	pair0_sock *s = p->psock;
+
+	nni_aio_cancel(&p->aio_send, NNG_ECANCELED);
+	nni_aio_cancel(&p->aio_recv, NNG_ECANCELED);
+	nni_aio_cancel(&p->aio_putq, NNG_ECANCELED);
+	nni_aio_cancel(&p->aio_getq, NNG_ECANCELED);
+
+	nni_mtx_lock(&s->mtx);
+	if (s->ppipe == p) {
+		s->ppipe = NULL;
+	}
+	nni_mtx_unlock(&s->mtx);
+}
+
+static void
+pair0_recv_cb(void *arg)
+{
+	pair0_pipe *p = arg;
+	pair0_sock *s = p->psock;
+	nni_msg *   msg;
+
+	if (nni_aio_result(&p->aio_recv) != 0) {
+		nni_pipe_stop(p->npipe);
+		return;
+	}
+
+	msg               = p->aio_recv.a_msg;
+	p->aio_putq.a_msg = msg;
+	p->aio_recv.a_msg = NULL;
+
+	nni_msg_set_pipe(msg, nni_pipe_id(p->npipe));
+	nni_msgq_aio_put(s->urq, &p->aio_putq);
+}
+
+static void
+pair0_putq_cb(void *arg)
+{
+	pair0_pipe *p = arg;
+
+	if (nni_aio_result(&p->aio_putq) != 0) {
+		nni_msg_free(p->aio_putq.a_msg);
+		p->aio_putq.a_msg = NULL;
+		nni_pipe_stop(p->npipe);
+		return;
+	}
+	nni_pipe_recv(p->npipe, &p->aio_recv);
+}
+
+static void
+pair0_getq_cb(void *arg)
+{
+	pair0_pipe *p = arg;
+	pair0_sock *s = p->psock;
+
+	if (nni_aio_result(&p->aio_getq) != 0) {
+		nni_pipe_stop(p->npipe);
+		return;
+	}
+
+	p->aio_send.a_msg = p->aio_getq.a_msg;
+	p->aio_getq.a_msg = NULL;
+	nni_pipe_send(p->npipe, &p->aio_send);
+}
+
+static void
+pair0_send_cb(void *arg)
+{
+	pair0_pipe *p = arg;
+	pair0_sock *s = p->psock;
+
+	if (nni_aio_result(&p->aio_send) != 0) {
+		nni_msg_free(p->aio_send.a_msg);
+		p->aio_send.a_msg = NULL;
+		nni_pipe_stop(p->npipe);
+		return;
+	}
+
+	nni_msgq_aio_get(s->uwq, &p->aio_getq);
+}
+
+static void
+pair0_sock_open(void *arg)
+{
+	NNI_ARG_UNUSED(arg);
+}
+
+static void
+pair0_sock_close(void *arg)
+{
+	NNI_ARG_UNUSED(arg);
+}
+
+static int
+pair0_sock_setopt(void *arg, int opt, const void *buf, size_t sz)
+{
+	pair0_sock *s = arg;
+	int         rv;
+
+	switch (opt) {
+	case NNG_OPT_RAW:
+		rv = nni_setopt_int(&s->raw, buf, sz, 0, 1);
+		break;
+	default:
+		rv = NNG_ENOTSUP;
+	}
+	return (rv);
+}
+
+static int
+pair0_sock_getopt(void *arg, int opt, void *buf, size_t *szp)
+{
+	pair0_sock *s = arg;
+	int         rv;
+
+	switch (opt) {
+	case NNG_OPT_RAW:
+		rv = nni_getopt_int(&s->raw, buf, szp);
+		break;
+	default:
+		rv = NNG_ENOTSUP;
+	}
+	return (rv);
+}
+
+static nni_proto_pipe_ops pair0_pipe_ops = {
+	.pipe_init  = pair0_pipe_init,
+	.pipe_fini  = pair0_pipe_fini,
+	.pipe_start = pair0_pipe_start,
+	.pipe_stop  = pair0_pipe_stop,
+};
+
+static nni_proto_sock_ops pair0_sock_ops = {
+	.sock_init   = pair0_sock_init,
+	.sock_fini   = pair0_sock_fini,
+	.sock_open   = pair0_sock_open,
+	.sock_close  = pair0_sock_close,
+	.sock_setopt = pair0_sock_setopt,
+	.sock_getopt = pair0_sock_getopt,
+};
+
+// Legacy protocol (v0)
+static nni_proto pair0_proto = {
+	.proto_version  = NNI_PROTOCOL_VERSION,
+	.proto_self     = { NNG_PROTO_PAIR_V0, "pair" },
+	.proto_peer     = { NNG_PROTO_PAIR_V0, "pair" },
+	.proto_flags    = NNI_PROTO_FLAG_SNDRCV,
+	.proto_sock_ops = &pair0_sock_ops,
+	.proto_pipe_ops = &pair0_pipe_ops,
+};
+
+int
+nng_pair0_open(nng_socket *sidp)
+{
+	return (nni_proto_open(sidp, &pair0_proto));
+}
diff --git a/src/protocol/pair/pair_v1.c b/src/protocol/pair/pair_v1.c
new file mode 100644
index 00000000..ea8c1226
--- /dev/null
+++ b/src/protocol/pair/pair_v1.c
@@ -0,0 +1,467 @@
+//
+// 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.
+//
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "core/nng_impl.h"
+
+// Pair protocol.  The PAIRv1 protocol is a simple 1:1 messaging pattern.
+
+typedef struct pair1_pipe pair1_pipe;
+typedef struct pair1_sock pair1_sock;
+
+static void pair1_sock_getq_cb(void *);
+static void pair1_pipe_send_cb(void *);
+static void pair1_pipe_recv_cb(void *);
+static void pair1_pipe_getq_cb(void *);
+static void pair1_pipe_putq_cb(void *);
+static void pair1_pipe_fini(void *);
+
+// pair1_sock is our per-socket protocol private structure.
+struct pair1_sock {
+	nni_sock *  nsock;
+	nni_msgq *  uwq;
+	nni_msgq *  urq;
+	int         raw;
+	int         ttl;
+	nni_mtx     mtx;
+	nni_idhash *pipes;
+	int         started;
+	int         poly;
+	nni_aio     aio_getq;
+	pair1_pipe *pipe; // cooked mode only
+};
+
+// pair1_pipe is our per-pipe protocol private structure.
+struct pair1_pipe {
+	nni_pipe *  npipe;
+	pair1_sock *psock;
+	nni_msgq *  sendq;
+	nni_aio     aio_send;
+	nni_aio     aio_recv;
+	nni_aio     aio_getq;
+	nni_aio     aio_putq;
+};
+
+static void
+pair1_sock_fini(void *arg)
+{
+	pair1_sock *s = arg;
+
+	nni_aio_fini(&s->aio_getq);
+	nni_idhash_fini(s->pipes);
+	nni_mtx_fini(&s->mtx);
+
+	NNI_FREE_STRUCT(s);
+}
+
+static int
+pair1_sock_init(void **sp, nni_sock *nsock)
+{
+	pair1_sock *s;
+	int         rv;
+
+	if ((s = NNI_ALLOC_STRUCT(s)) == NULL) {
+		return (NNG_ENOMEM);
+	}
+	// Raw mode uses this.
+	if (((rv = nni_aio_init(&s->aio_getq, pair1_sock_getq_cb, s)) != 0) ||
+	    ((rv = nni_mtx_init(&s->mtx)) != 0) ||
+	    ((rv = nni_idhash_init(&s->pipes)) != 0)) {
+		pair1_sock_fini(s);
+	} else {
+		s->nsock = nsock;
+		s->raw   = 0;
+		s->poly  = 0;
+		s->uwq   = nni_sock_sendq(nsock);
+		s->urq   = nni_sock_recvq(nsock);
+		s->ttl   = 8;
+		*sp      = s;
+	}
+	return (0);
+}
+
+static int
+pair1_pipe_init(void **pp, nni_pipe *npipe, void *psock)
+{
+	pair1_pipe *p;
+	int         rv;
+
+	if ((p = NNI_ALLOC_STRUCT(p)) == NULL) {
+		return (NNG_ENOMEM);
+	}
+	if (((rv = nni_msgq_init(&p->sendq, 2)) != 0) ||
+	    ((rv = nni_aio_init(&p->aio_send, pair1_pipe_send_cb, p)) != 0) ||
+	    ((rv = nni_aio_init(&p->aio_recv, pair1_pipe_recv_cb, p)) != 0) ||
+	    ((rv = nni_aio_init(&p->aio_getq, pair1_pipe_getq_cb, p)) != 0) ||
+	    ((rv = nni_aio_init(&p->aio_putq, pair1_pipe_putq_cb, p)) != 0)) {
+		pair1_pipe_fini(p);
+	} else {
+		p->npipe = npipe;
+		p->psock = psock;
+		*pp      = p;
+	}
+	return (rv);
+}
+
+static void
+pair1_pipe_fini(void *arg)
+{
+	pair1_pipe *p = arg;
+	nni_aio_fini(&p->aio_send);
+	nni_aio_fini(&p->aio_recv);
+	nni_aio_fini(&p->aio_putq);
+	nni_aio_fini(&p->aio_getq);
+	nni_msgq_fini(p->sendq);
+	NNI_FREE_STRUCT(p);
+}
+
+static int
+pair1_pipe_start(void *arg)
+{
+	pair1_pipe *p = arg;
+	pair1_sock *s = p->psock;
+	uint32_t    id;
+	int         rv;
+
+	id = nni_pipe_id(p->npipe);
+	if ((rv = nni_idhash_insert(s->pipes, id, p)) != 0) {
+		return (rv);
+	}
+	nni_mtx_lock(&s->mtx);
+	if (!s->poly) {
+		if (s->pipe != NULL) {
+			nni_mtx_unlock(&s->mtx);
+			nni_idhash_remove(s->pipes, id);
+			return (NNG_EBUSY);
+		}
+	} else {
+		if (!s->started) {
+			nni_msgq_aio_get(s->uwq, &s->aio_getq);
+		}
+	}
+
+	s->pipe    = p;
+	s->started = 1;
+	nni_mtx_unlock(&s->mtx);
+
+	// Schedule a getq.  In polyamorous mode we get on the per pipe
+	// sendq, as the socket distributes to us. In monogamous mode we
+	// bypass and get from the upper writeq directly (saving a set of
+	// context switches).
+	if (s->poly) {
+		nni_msgq_aio_get(p->sendq, &p->aio_getq);
+	} else {
+		nni_msgq_aio_get(s->uwq, &p->aio_getq);
+	}
+	// And the pipe read of course.
+	nni_pipe_recv(p->npipe, &p->aio_recv);
+
+	return (0);
+}
+
+static void
+pair1_pipe_stop(void *arg)
+{
+	pair1_pipe *p = arg;
+	pair1_sock *s = p->psock;
+
+	nni_msgq_close(p->sendq);
+	nni_aio_cancel(&p->aio_send, NNG_ECANCELED);
+	nni_aio_cancel(&p->aio_recv, NNG_ECANCELED);
+	nni_aio_cancel(&p->aio_putq, NNG_ECANCELED);
+	nni_aio_cancel(&p->aio_getq, NNG_ECANCELED);
+
+	nni_mtx_lock(&s->mtx);
+	if (s->pipe == p) {
+		s->pipe = NULL;
+	}
+	nni_mtx_unlock(&s->mtx);
+	nni_idhash_remove(s->pipes, nni_pipe_id(p->npipe));
+}
+
+static void
+pair1_pipe_recv_cb(void *arg)
+{
+	pair1_pipe *p = arg;
+	pair1_sock *s = p->psock;
+	nni_msg *   msg;
+	uint32_t    hdr;
+	nni_pipe *  npipe = p->npipe;
+	int         rv;
+
+	if (nni_aio_result(&p->aio_recv) != 0) {
+		nni_pipe_stop(p->npipe);
+		return;
+	}
+
+	msg               = p->aio_recv.a_msg;
+	p->aio_recv.a_msg = NULL;
+
+	// Store the pipe ID.
+	nni_msg_set_pipe(msg, nni_pipe_id(p->npipe));
+
+	// If the message is missing the hop count header, scrap it.
+	if (nni_msg_len(msg) < sizeof(uint32_t)) {
+		nni_msg_free(msg);
+		nni_pipe_stop(npipe);
+		return;
+	}
+	hdr = nni_msg_trim_u32(msg);
+	if (hdr & 0xffffff00) {
+		nni_msg_free(msg);
+		nni_pipe_stop(npipe);
+		return;
+	}
+
+	// If we bounced too many times, discard the message, but
+	// keep getting more.
+	if (hdr >= s->ttl) {
+		nni_msg_free(msg);
+		nni_pipe_recv(npipe, &p->aio_recv);
+		return;
+	}
+
+	// Store the pipe id followed by the hop count.
+	if ((rv = nni_msg_header_append_u32(msg, hdr)) != 0) {
+		nni_msg_free(msg);
+		nni_pipe_recv(npipe, &p->aio_recv);
+		return;
+	}
+
+	// Send the message up.
+	p->aio_putq.a_msg = msg;
+	nni_msgq_aio_put(s->urq, &p->aio_putq);
+}
+
+static void
+pair1_sock_getq_cb(void *arg)
+{
+	pair1_pipe *p;
+	pair1_sock *s = arg;
+	nni_msg *   msg;
+	uint32_t    id;
+
+	if (nni_aio_result(&s->aio_getq) != 0) {
+		// Socket closing...
+		return;
+	}
+
+	msg               = s->aio_getq.a_msg;
+	s->aio_getq.a_msg = NULL;
+
+	// By definition we are in polyamorous mode.
+	NNI_ASSERT(s->poly);
+
+	nni_mtx_lock(&s->mtx);
+
+	// If no pipe was requested, we look for any connected peer.
+	if (((id = nni_msg_get_pipe(msg)) == 0) && (s->pipe != NULL)) {
+		id = nni_pipe_id(s->pipe->npipe);
+	}
+
+	if (nni_idhash_find(s->pipes, id, (void **) &p) != 0) {
+		// Pipe not present!
+		nni_mtx_unlock(&s->mtx);
+		nni_msg_free(msg);
+		nni_msgq_aio_get(s->uwq, &s->aio_getq);
+		return;
+	}
+
+	// Try a non-blocking send.  If this fails we just discard the
+	// message.  We have to do this to avoid head-of-line blocking
+	// for messages sent to other pipes.  Note that there is some
+	// buffering in the sendq.
+	if (nni_msgq_tryput(p->sendq, msg) != 0) {
+		nni_msg_free(msg);
+	}
+
+	nni_mtx_unlock(&s->mtx);
+	nni_msgq_aio_get(s->uwq, &s->aio_getq);
+}
+
+static void
+pair1_pipe_putq_cb(void *arg)
+{
+	pair1_pipe *p = arg;
+
+	if (nni_aio_result(&p->aio_putq) != 0) {
+		nni_msg_free(p->aio_putq.a_msg);
+		p->aio_putq.a_msg = NULL;
+		nni_pipe_stop(p->npipe);
+		return;
+	}
+	nni_pipe_recv(p->npipe, &p->aio_recv);
+}
+
+static void
+pair1_pipe_getq_cb(void *arg)
+{
+	pair1_pipe *p = arg;
+	pair1_sock *s = p->psock;
+	nni_msg *   msg;
+	uint32_t    hops;
+	uint8_t *   data;
+
+	if (nni_aio_result(&p->aio_getq) != 0) {
+		nni_pipe_stop(p->npipe);
+		return;
+	}
+
+	msg               = p->aio_getq.a_msg;
+	p->aio_getq.a_msg = NULL;
+
+	// Raw mode messages have the header already formed, with
+	// a hop count.  Cooked mode messages have no
+	// header so we have to add one.
+	if (s->raw) {
+		if (nni_msg_header_len(msg) != sizeof(uint32_t)) {
+			goto badmsg;
+		}
+		hops = nni_msg_header_trim_u32(msg);
+	} else {
+		hops = 0;
+	}
+
+	hops++;
+
+	// Insert the hops header.
+	if (nni_msg_header_append_u32(msg, hops) != 0) {
+		goto badmsg;
+	}
+
+	p->aio_send.a_msg = msg;
+	nni_pipe_send(p->npipe, &p->aio_send);
+	return;
+
+badmsg:
+	nni_msg_free(msg);
+	nni_msgq_aio_get(s->poly ? p->sendq : s->uwq, &p->aio_getq);
+}
+
+static void
+pair1_pipe_send_cb(void *arg)
+{
+	pair1_pipe *p = arg;
+	pair1_sock *s = p->psock;
+
+	if (nni_aio_result(&p->aio_send) != 0) {
+		nni_msg_free(p->aio_send.a_msg);
+		p->aio_send.a_msg = NULL;
+		nni_pipe_stop(p->npipe);
+		return;
+	}
+
+	// In polyamorous mode, we want to get from the sendq; in
+	// monogamous we get from upper writeq.
+	if (s->poly) {
+		nni_msgq_aio_get(p->sendq, &p->aio_getq);
+	} else {
+		nni_msgq_aio_get(s->uwq, &p->aio_getq);
+	}
+}
+
+static void
+pair1_sock_open(void *arg)
+{
+	NNI_ARG_UNUSED(arg);
+}
+
+static void
+pair1_sock_close(void *arg)
+{
+	NNI_ARG_UNUSED(arg);
+}
+
+static int
+pair1_sock_setopt(void *arg, int opt, const void *buf, size_t sz)
+{
+	pair1_sock *s = arg;
+	int         rv;
+
+	nni_mtx_lock(&s->mtx);
+	switch (opt) {
+	case NNG_OPT_RAW:
+		if (s->started) {
+			rv = NNG_ESTATE;
+		} else {
+			rv = nni_setopt_int(&s->raw, buf, sz, 0, 1);
+		}
+		break;
+	case NNG_OPT_POLYAMOROUS:
+		if (s->started) {
+			rv = NNG_ESTATE;
+		} else {
+			rv = nni_setopt_int(&s->poly, buf, sz, 0, 1);
+		}
+		break;
+	case NNG_OPT_MAXTTL:
+		rv = nni_setopt_int(&s->ttl, buf, sz, 0, 255);
+		break;
+	default:
+		rv = NNG_ENOTSUP;
+	}
+
+	nni_mtx_unlock(&s->mtx);
+	return (rv);
+}
+
+static int
+pair1_sock_getopt(void *arg, int opt, void *buf, size_t *szp)
+{
+	pair1_sock *s = arg;
+	int         rv;
+
+	nni_mtx_lock(&s->mtx);
+	switch (opt) {
+	case NNG_OPT_RAW:
+		rv = nni_getopt_int(&s->raw, buf, szp);
+		break;
+	case NNG_OPT_MAXTTL:
+		rv = nni_getopt_int(&s->ttl, buf, szp);
+		break;
+	default:
+		rv = NNG_ENOTSUP;
+	}
+	nni_mtx_unlock(&s->mtx);
+	return (rv);
+}
+
+static nni_proto_pipe_ops pair1_pipe_ops = {
+	.pipe_init  = pair1_pipe_init,
+	.pipe_fini  = pair1_pipe_fini,
+	.pipe_start = pair1_pipe_start,
+	.pipe_stop  = pair1_pipe_stop,
+};
+
+static nni_proto_sock_ops pair1_sock_ops = {
+	.sock_init   = pair1_sock_init,
+	.sock_fini   = pair1_sock_fini,
+	.sock_open   = pair1_sock_open,
+	.sock_close  = pair1_sock_close,
+	.sock_setopt = pair1_sock_setopt,
+	.sock_getopt = pair1_sock_getopt,
+};
+
+static nni_proto pair1_proto = {
+	.proto_version  = NNI_PROTOCOL_VERSION,
+	.proto_self     = { NNG_PROTO_PAIR_V1, "pair1" },
+	.proto_peer     = { NNG_PROTO_PAIR_V1, "pair1" },
+	.proto_flags    = NNI_PROTO_FLAG_SNDRCV,
+	.proto_sock_ops = &pair1_sock_ops,
+	.proto_pipe_ops = &pair1_pipe_ops,
+};
+
+int
+nng_pair1_open(nng_socket *sidp)
+{
+	return (nni_proto_open(sidp, &pair1_proto));
+}