Scroll to navigation



zmq_ctx_get - get context options


int zmq_ctx_get (void *context, int option_name);


The zmq_ctx_get() function shall return the option specified by the option_name argument.

The zmq_ctx_get() function accepts the following option names:

ZMQ_IO_THREADS: Get number of I/O threads

The ZMQ_IO_THREADS argument returns the size of the 0MQ thread pool for this context.

ZMQ_MAX_SOCKETS: Get maximum number of sockets

The ZMQ_MAX_SOCKETS argument returns the maximum number of sockets allowed for this context.

ZMQ_MAX_MSGSZ: Get maximum message size

The ZMQ_MAX_MSGSZ argument returns the maximum size of a message allowed for this context. Default value is INT_MAX.

ZMQ_ZERO_COPY_RECV: Get message decoding strategy

The ZMQ_ZERO_COPY_RECV argument return whether message decoder uses a zero copy strategy when receiving messages. Default value is 1. NOTE: in DRAFT state, not yet available in stable releases.

ZMQ_SOCKET_LIMIT: Get largest configurable number of sockets

The ZMQ_SOCKET_LIMIT argument returns the largest number of sockets that zmq_ctx_set(3) will accept.

ZMQ_IPV6: Set IPv6 option

The ZMQ_IPV6 argument returns the IPv6 option for the context.

ZMQ_BLOCKY: Get blocky setting

The ZMQ_BLOCKY argument returns 1 if the context will block on terminate, zero if the "block forever on context termination" gambit was disabled by setting ZMQ_BLOCKY to false on all new contexts.

ZMQ_THREAD_SCHED_POLICY: Get scheduling policy for I/O threads

The ZMQ_THREAD_SCHED_POLICY argument returns the scheduling policy for internal context’s thread pool.

ZMQ_THREAD_NAME_PREFIX: Get name prefix for I/O threads

The ZMQ_THREAD_NAME_PREFIX argument gets the numeric prefix of each thread created for the internal context’s thread pool.

ZMQ_MSG_T_SIZE: Get the zmq_msg_t size at runtime

The ZMQ_MSG_T_SIZE argument returns the size of the zmq_msg_t structure at runtime, as defined in the include/zmq.h public header. This is useful for example for FFI bindings that can’t simply do a sizeof().


The zmq_ctx_get() function returns a value of 0 or greater if successful. Otherwise it returns -1 and sets errno to one of the values defined below.



The requested option option_name is unknown.


The provided context is invalid.


Setting a limit on the number of sockets.

void *context = zmq_ctx_new ();
zmq_ctx_set (context, ZMQ_MAX_SOCKETS, 256);
int max_sockets = zmq_ctx_get (context, ZMQ_MAX_SOCKETS);
assert (max_sockets == 256);

Switching off the context deadlock gambit.

zmq_ctx_set (ctx, ZMQ_BLOCKY, false);


zmq_ctx_set(3) zmq(7)


This page was written by the 0MQ community. To make a change please read the 0MQ Contribution Policy at

10/09/2023 0MQ 4.3.5