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Man Pages

Manual Reference Pages  -  ZSTR (3)

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zstr - sending and receiving strings



//  Receive C string from socket. Caller must free returned string using
//  zstr_free(). Returns NULL if the context is being terminated or the
//  process was interrupted.
    zstr_recv (void *source);

// Send a C string to a socket, as a frame. The string is sent without // trailing null byte; to read this you can use zstr_recv, or a similar // method that adds a null terminator on the received string. String // may be NULL, which is sent as "". CZMQ_EXPORT int zstr_send (void *dest, const char *string);

// Send a C string to a socket, as zstr_send(), with a MORE flag, so that // you can send further strings in the same multi-part message. CZMQ_EXPORT int zstr_sendm (void *dest, const char *string);

// Send a formatted string to a socket. Note that you should NOT use // user-supplied strings in the format (they may contain % which // will create security holes). CZMQ_EXPORT int zstr_sendf (void *dest, const char *format, ...);

// Send a formatted string to a socket, as for zstr_sendf(), with a // MORE flag, so that you can send further strings in the same multi-part // message. CZMQ_EXPORT int zstr_sendfm (void *dest, const char *format, ...);

// Send a series of strings (until NULL) as multipart data // Returns 0 if the strings could be sent OK, or -1 on error. CZMQ_EXPORT int zstr_sendx (void *dest, const char *string, ...);

// Receive a series of strings (until NULL) from multipart data. // Each string is allocated and filled with string data; if there // are not enough frames, unallocated strings are set to NULL. // Returns -1 if the message could not be read, else returns the // number of strings filled, zero or more. Free each returned string // using zstr_free(). If not enough strings are provided, remaining // multipart frames in the message are dropped. CZMQ_EXPORT int zstr_recvx (void *source, char **string_p, ...);

// Free a provided string, and nullify the parent pointer. Safe to call on // a null pointer. CZMQ_EXPORT void zstr_free (char **string_p);

// Self test of this class CZMQ_EXPORT void zstr_test (bool verbose);


The zstr class provides utility functions for sending and receiving C strings across 0MQ sockets. It sends strings without a terminating null, and appends a null byte on received strings. This class is for simple message sending.

       Memory                       Wire
       +-------------+---+          +---+-------------+
Send   | S t r i n g | 0 |  ---->   | 6 | S t r i n g |
       +-------------+---+          +---+-------------+

       Wire                         Heap
       +---+-------------+          +-------------+---+
Recv   | 6 | S t r i n g |  ---->   | S t r i n g | 0 |
       +---+-------------+          +-------------+---+


From zstr_test method.

//  Create two PAIR sockets and connect over inproc
zsock_t *output = zsock_new_pair ("@inproc://zstr.test");
assert (output);
zsock_t *input = zsock_new_pair (">inproc://zstr.test");
assert (input);

// Send ten strings, five strings with MORE flag and then END int string_nbr; for (string_nbr = 0; string_nbr < 10; string_nbr++) zstr_sendf (output, "this is string %d", string_nbr); zstr_sendx (output, "This", "is", "almost", "the", "very", "END", NULL);

// Read and count until we receive END string_nbr = 0; for (string_nbr = 0;; string_nbr++) { char *string = zstr_recv (input); assert (string); if (streq (string, "END")) { zstr_free (&string); break; } zstr_free (&string); } assert (string_nbr == 15);

zsock_destroy (&input); zsock_destroy (&output);


The czmq manual was written by the authors in the AUTHORS file.


Main web site: \m[blue] \m[]

Report bugs to the email <\m[blue]\m[][1]>


Copyright (c) 1991-2012 iMatix Corporation -- Copyright other contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for 0MQ: This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at LICENSE included with the czmq distribution.


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CZMQ 3&.0&.1 ZSTR (3) 06/01/2015

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