Migrating from NNG 1.x

There are some incompatibities from NNG 1.x, and applications must make certain changes for NNG 2.0. This guide should help with this migration. While we have made reasonable efforts to highlight all of the things that applications could run into, this list is not necessarily exhaustive, and undocumented interfaces may have changed without notice here.

Detecting NNG v2

For applications that need to detect NNG v2 versus older code, the NNG_MAJOR_VERSION macro can be used. This will have numeric value 2 for version 2, and 1 for earlier versions.

note

NNG version 2.0 is not stabilized yet, and while it is in development there is no compatibility guarantee between releases or builds of NNG 2.

Nanomsg Compatibility

Applications using the legacy libnanomsg API will have to be updated to native NNG interfaces. See the Migrating From libnanomsg chapter for details.

Library Initialization

It is now required for applications to initialize the library explicitly before using it. This is done using the nng_init function.

Removed Headers

The following header files are removed, and the declarations they provided are now provided by including <nng/nng.h>. Simply remove any references to them.

nng/protocol/bus0/bus.h
nng/protocol/pair0/pair.h
nng/protocol/pair1/pair.h
nng/protocol/pipeline0/pull.h
nng/protocol/pipeline0/push.h
nng/protocol/pubsub0/pub.h
nng/protocol/pubsub0/sub.h
nng/protocol/reqrep0/rep.h
nng/protocol/reqrep0/req.h
nng/protocol/survey0/respond.h
nng/protocol/survey0/survey.h
nng/supplemental/tls/tls.h
nng/supplemental/util/idhash.h
nng/supplemental/util/platform.h
nng/transport/inproc/inproc.h
nng/transport/ipc/ipc.h
nng/transport/tcp/tcp.h
nng/transport/tls/tls.h
nng/transport/ws/websocket.h
nng/transport/zerotier/zerotier.h

Renamed Functions

The following functions have been renamed as described by the following table. The old names are available by defining the macro NNG1_TRANSITION in your compilation environment.

Old Name	New Name
`nng_close`	`nng_socket_close`
`nng_recv_aio`	`nng_socket_recv`
`nng_send_aio`	`nng_socket_send`

Removed Protocol Aliases

The following macro aliases are removed, unless NNG1_TRANSITION is defined in your compilation environment.

nng_bus_open
nng_pair_open
nng_pub_open
nng_pull_open
nng_push_open
nng_rep_open
nng_req_open
nng_respondent_open
nng_sub_open
nng_surveyor_open

Just add either 0 or 1 (in the case of PAIRv1) to get the protocol desired. (Forcing the version number to be supplied should avoid surprises later as new versions of protocols are added.)

NNG_FLAG_ALLOC Removed

The NNG_FLAG_ALLOC flag that allowed a zero copy semantic with nng_send and nng_recv is removed. This was implemented mostly to aid legacy nanomsg applications, and it was both error prone and still a bit suboptimal in terms of performance.

Modern code should use one of nng_sendmsg, nng_recvmsg, nng_socket_send, or nng_socket_recv to get the maximum performance benefit. Working directly with nng_msg structures gives more control, reduces copies, and reduces allocation activity.

Error Code Changes

When an operation fails with NNG_ESTOPPED, it means that the associated [nni_aio] object has been permanently stopped and must not be reused. Applications must watch for this error code, and not resubmit an operation that returns it. This is particularly important for callbacks that automatically resubmit operations. Failure to observe this rule will lead to an infinite loop as any further operations on the object will fail immediately with NNG_ESTOPPED.

The error codes NNG_EAMBIGUOUS and NNG_ENOARG have been removed.

AIO Provider API changes

The API used for providers for asynchronous I/O operations has changed slightly.

The nng_aio_begin function is removed. However a new nng_aio_reset function should be called instead, before performing any other operations on an aio object. (This simply clears certain fields.)
The nng_aio_defer function is replaced, with a very nng_aio_start function. However, this function has slightly different semantics. It will automatically call the callback if the operation cannot be scheduled.
Be aware of the new NNG_ESTOPPED error code, for operations on a handle that is being torn down by the consumer.

Transport Specific Functions

Transports have not needed to be registered for a long time now, and the functions for doing so have been removed. These functions can be simply removed from your application:

nng_inproc_register
nng_ipc_register
nng_tls_register
nng_tcp_register
nng_ws_register
nng_wss_register
nng_zt_register

Additionally, the header files containing these functions have been removed, such as nng/transport/ipc/ipc.h. Simply remove #include references to those files.

TLS Configuration

The support for configuring TLS via NNG_OPT_TLS_CONFIG, NNG_TLS_AUTH_MODE, NNG_OPT_TLS_CA_FILE, NNG_OPT_TLS_SERVER_NAME, and similar has been removed.

Instead configuration must be performed by allocating a nng_tls_config object, and then setting fields on it using the appropriate functions, after which it may be configured on a listener or dialer using the nng_listener_set_tls or nng_dialer_set_tls functions.

Likewise, when using the streams API, use the nng_stream_listener_set_tls or nng_stream_dialer_set_tls functions.

Note that the declarations needed for TLS configuration are now available in <nng/nng.h>, rather than the supplemental header.

Old TLS Versions Removed

Support for very old TLS versions 1.0 and 1.1 is removed. Further, the NNG_TLS_1_0 and NNG_TLS_1_1 constants are also removed. Applications should use NNG_TLS_1_2 or even NNG_TLS_1_3 instead.

Only One TLS Key/Cert Per Configuration

The ability to configure multiple keys and certificates for a given TLS configuration object is removed. (The nng_tls_config_own_cert will return NNG_EBUSY if it has already been called for the configuration.) The intended purpose was to support alternative cryptographic algorithms, but this is not necessary, was never used, and was error prone.

Support for Local Addresses in Dial URLs Removed

NNG 1.x had an undocumented ability to specify the local address to bind to when dialing, by using the local address in front of the destination address separated by a semicolon. This was provided for legacy libnanomsg compatilibility, and is no longer offered. The correct way to specify a local address is by setting NNG_OPT_LOCADDR on the dialer.

IPC Option Type Changes

The types of NNG_OPT_PEER_GID, NNG_OPT_PEER_PID, NNG_OPT_PEER_UID, and NNG_OPT_PEER_ZONEID have changed from uint64_t to int. The underlying platforms all use 32-bit quantities for these.

Option Functions

The previously deprecated nng_pipe_getopt_xxx family of functions is removed. Applications should use nng_pipe_get and related functions instead.

The socket option function families for nng_getopt and nng_setopt have been removed as well. In this case, use the nng_socket_get and nng_socket_set functions as appropriate.

The _getopt and _setopt functions for contexts, listeners, and dialers are no longer present. Simply changing _getopt to _get or _setopt to _set in the function name should be sufficient in most cases.

The following functions served no useful purpose (after other changes described in this document), and are thus removed:

nng_ctx_get_string
nng_ctx_set_string
nng_ctx_get_uint64
nng_dialer_get_ptr
nng_dialer_set_ptr
nng_dialer_get_uint64
nng_dialer_set_uint64
nng_listener_get_ptr
nng_listener_set_ptr
nng_listener_get_uint64
nng_listener_set_uint64
nng_socket_get_ptr
nng_socket_set_ptr
nng_socket_get_string
nng_socket_set_string
nng_socket_get_uint64
nng_socket_set_uint64
nng_stream_get_ptr
nng_stream_set_ptr
nng_stream_get_uint64
nng_stream_dialer_get_ptr
nng_stream_dialer_set_ptr
nng_stream_dialer_get_uint64
nng_stream_dialer_set_uint64
nng_stream_listener_get_ptr
nng_stream_listener_set_ptr
nng_stream_listener_get_uint64
nng_stream_listener_set_uint64
nng_ctx_get_ptr (not documented)
nng_ctx_set_ptr (not documented)

Untyped Option Functions Removed

The following functions are removed. To access options, use a proper typed access function, such as one ending in a suffix like _bool (to access a bool typed option).

nng_ctx_get
nng_ctx_set
nng_dialer_get
nng_dialer_set
nng_listener_get
nng_listener_set
nng_pipe_get
nng_socket_get
nng_socket_set
nng_stream_get
nng_stream_set
nng_stream_dialer_get
nng_stream_dialer_set
nng_stream_listener_get
nng_stream_listener_set

Stream Options

The ability to set options on streams after they have been created is no longer present. (It turns out that this was not very useful.) All functions nng_stream_set_xxx are removed. For tuning the NNG_OPT_TCP_NODELAY or similar properties, set the option on the listener or dialer that creates the stream instead.

Transport Options

A number of transport options can no longer be set on the socket. Instead these options must be set on the endpoint (dialer or listener) using the appropriate nng_dialer_set or nng_listener_set option. This likely means that it is necessary to allocate and configure the endpoint before attaching it to the socket. This will also afford a much more fine-grained level of control over transport options.

The following options are copied from the socket when creating a dialer or listener, but afterwards will not be changed on the dialer or listener if the socket changes. It is recommended to set them properly on the socket before creating dialers or listeners, or set them explicitly on the dialer or listener directly:

The latter option is a hint for transports and intended to facilitate early detection (and possibly avoidance of extra allocations) of oversize messages, before bringing them into the socket itself.

Socket Options

The NNG_OPT_PROTO, NNG_OPT_PROTONAME, NNG_OPT_PEER, and NNG_OPT_PEERNAME options have been replaced by functions instead of options. Use nng_socket_proto_id, nng_socket_peer_id, nng_socket_proto_name, and nng_socket_peer_name instead. Note that the new functions provide a reference to a static string, and thus do not require allocation, and the returned strings should not be freed. Also the IDs are provided as uint16_t, matching the actual wire protocol values, instead of int.

The NNG_OPT_RAW option has aso been replaced by a function, nng_socket_raw.

The NNG_OPT_SENDFD and NNG_OPT_RECVFD options have been replaced by nng_socket_get_send_poll_fd and nng_socket_get_recv_poll_fd respectively.

The NNG_OPT_SOCKNAME function is removed. This was provided for application use, and never used internally by NNG. Applications should keep track of this information separately.

Subscriptions

The NNG_OPT_SUB_SUBSCRIBE and NNG_OPT_SUB_UNSUBCRIBE options have been replaced by the following functions: nng_sub0_socket_subscribe, nng_sub0_socket_unsubscribe, nng_sub0_ctx_subscribe and nng_sub0_ctx_unsubscribe. These functions, like the options they replace, are only applicable to SUB sockets.

Statistics Use Constified Pointers

A number of the statistics functions take, or return, const nng_stat * instead of plain nng_stat *. The ABI has not changed, but it may be necessary to declare certain methods variables const to avoid warnings about misuse of const.

Wildcards Not Valid in URLs

The use of * to act as a wild card meaning all local interface addresses is removed. The empty string already performs this function, and unlike * is RFC compliant.

URL Option Removed

The NNG_OPT_URL option has been removed. It is replaced by the type safe nng_dialer_get_url and nng_listener_get_url functions, which return an nng_url structure instead of a string.

URL Structure Changes

The details of nng_url have changed significantly, and direct access of the structure is no longer permitted. Intead new accessors functions are provided:

u_scheme is replaced by nng_url_scheme.
u_port is replaced by nng_url_port, but this returns a uint16_t.
u_hostname is replaced by nng_url_hostname.
u_path is replaced by nng_url_path.
u_query is replaced by nng_url_query.
u_fragment is replaced by nng_url_fragment.
u_userinfo is replaced by nng_url_userinfo.
u_requri is removed - it can be easily formulated from the other fields.
u_host is removed - use nng_url_hostname and nng_url_port to construct if needed
u_rawurl is removed - a “cooked” URL can be obtained from the new nng_url_sprintf function.

HTTP API

The entire HTTP API has been refactored and should be much simpler to use and more efficient. Applications directly using the HTTP API will need to be fully modified.

A few limits on string lengths of certain values are now applied, which allows us to preallocate values and eliminate certain unreasonable error paths. If values longer than these are supplied in certain APIs they may be silently truncated to the limit:

Hostnames are limited per RFC 1035 to 253 characters (not including terminating “.” or zero byte.)
HTTP Method names are limited to 32 bytes (the longest IANA registered method is currently 18 bytes, used for WebDAV.)
The fixed part of URI pathnames used with HTTP handlers is limited to 1024 bytes. (Longer URIs may be accepted by using [nng_http_handler_set_tree] and matching a parent of the directory component.)

The following API calls have changed so that they are void returns, and cannot fail. They may silently truncate data.

[nng_http_req_set_method]
[nng_http_res_set_status]
[nng_http_handler_collect_body]
[nng_http_handler_set_data]
[nng_http_handler_set_host]
[nng_http_handler_set_method]
[nng_http_handler_set_tree]

The HTTP handler objects may not be modified once in use. Previously this would fail with NNG_EBUSY. These checks are removed now, but debug builds will assert if an application tries to do so.

WebSocket API

The NNG_OPT_WSS_REQUEST_HEADERS, NNG_OPT_WSS_RESPONSE_HEADERS and NNG_OPT_WS_OPT_WS_REQUEST_HEADERS, NNG_OPT_WS_RESPONSE_HEADERS have been removed.

The NNG_OPT_WS_REQUEST_HEADER and NNG_OPT_WS_RESPONSE_HEADER option prefixes have been collapsed into just NNG_OPT_WS_HEADER, with slightly different semantics. It still is a prefix (append the name of the header of interest), but setting it can only affect outbound headers (request header for dialers, response header for listeners), and when reading it on a pipe, the value returned is the header sent by the remote peer.

The undocumented hook function signature has changed to reflect changes in the HTTP API.

NNG Reference Manual (DRAFT)