ZPROXY(3)

NAME
zproxy - Class for run a steerable proxy in the background

SYNOPSIS

//  Create new zproxy actor instance. The proxy switches messages between
//  a frontend socket and a backend socket; use the FRONTEND and BACKEND
//  commands to configure these:
//
//      zactor_t *proxy = zactor_new (zproxy, NULL);
//
//  Destroy zproxy instance. This destroys the two sockets and stops any
//  message flow between them:
//
//      zactor_destroy (&proxy);
//
//  Note that all zproxy commands are synchronous, so your application always
//  waits for a signal from the actor after each command.
//
//  Enable verbose logging of commands and activity:
//
//      zstr_send (proxy, "VERBOSE");
//      zsock_wait (proxy);
//
//  Specify frontend socket type -- see zsock_type_str () -- and attach to
//  endpoints, see zsock_attach (). Note that a proxy socket is always
//  serverish:
//
//      zstr_sendx (proxy, "FRONTEND", "XSUB", endpoints, NULL);
//      zsock_wait (proxy);
//
//  When the socket type is XSUB or SUB, topic(s) string(s) can be passed as
//  additional arguments (NOTE: in DRAFT state) and the socket will subscribe
//  using them.
//
//  Specify backend socket type -- see zsock_type_str () -- and attach to
//  endpoints, see zsock_attach (). Note that a proxy socket is always
//  serverish:
//
//      zstr_sendx (proxy, "BACKEND", "XPUB", endpoints, NULL);
//      zsock_wait (proxy);
//
//  Capture all proxied messages; these are delivered to the application
//  via an inproc PULL socket that you have already bound to the specified
//  endpoint:
//
//      zstr_sendx (proxy, "CAPTURE", endpoint, NULL);
//      zsock_wait (proxy);
//
//  Pause the proxy. A paused proxy will cease processing messages, causing
//  them to be queued up and potentially hit the high-water mark on the
//  frontend or backend socket, causing messages to be dropped, or writing
//  applications to block:
//
//      zstr_sendx (proxy, "PAUSE", NULL);
//      zsock_wait (proxy);
//
//  Resume the proxy. Note that the proxy starts automatically as soon as it
//  has a properly attached frontend and backend socket:
//
//      zstr_sendx (proxy, "RESUME", NULL);
//      zsock_wait (proxy);
//
//  Configure an authentication domain for the "FRONTEND" or "BACKEND" proxy
//  socket -- see zsock_set_zap_domain (). Call before binding socket:
//
//      zstr_sendx (proxy, "DOMAIN", "FRONTEND", "global", NULL);
//      zsock_wait (proxy);
//
//  Configure PLAIN authentication for the "FRONTEND" or "BACKEND" proxy
//  socket -- see zsock_set_plain_server (). Call before binding socket:
//
//      zstr_sendx (proxy, "PLAIN", "BACKEND", NULL);
//      zsock_wait (proxy);
//
//  Configure CURVE authentication for the "FRONTEND" or "BACKEND" proxy
//  socket -- see zsock_set_curve_server () -- specifying both the public and
//  secret keys of a certificate as Z85 armored strings -- see
//  zcert_public_txt () and zcert_secret_txt (). Call before binding socket:
//
//      zstr_sendx (proxy, "CURVE", "FRONTEND", public_txt, secret_txt, NULL);
//      zsock_wait (proxy);
//
//  This is the zproxy constructor as a zactor_fn; the argument is a
//  character string specifying frontend and backend socket types as two
//  uppercase strings separated by a hyphen:
CZMQ_EXPORT void
    zproxy (zsock_t *pipe, void *unused);
//  Selftest
CZMQ_EXPORT void
    zproxy_test (bool verbose);
Please add '@interface' section in '/home/builder/.termux-build/libczmq/src/doc/../src/zproxy.c'.

DESCRIPTION

A zproxy actor switches messages between a frontend and a backend socket. It acts much like the zmq_proxy_steerable method, though it makes benefit of CZMQ’s facilities, to be somewhat simpler to set-up.

This class replaces zproxy_v2, and is meant for applications that use the CZMQ v3 API (meaning, zsock).

EXAMPLE

From zproxy_test method.

    //  Create and configure our proxy
    zactor_t *proxy = zactor_new (zproxy, NULL);
    assert (proxy);
    if (verbose) {
        zstr_sendx (proxy, "VERBOSE", NULL);
        zsock_wait (proxy);
    }
    zstr_sendx (proxy, "FRONTEND", "PULL", "inproc://frontend", NULL);
    zsock_wait (proxy);
    zstr_sendx (proxy, "BACKEND", "PUSH", "inproc://backend", NULL);
    zsock_wait (proxy);
    //  Connect application sockets to proxy
    zsock_t *faucet = zsock_new_push (">inproc://frontend");
    assert (faucet);
    zsock_t *sink = zsock_new_pull (">inproc://backend");
    assert (sink);
    //  Send some messages and check they arrived
    char *hello, *world;
    zstr_sendx (faucet, "Hello", "World", NULL);
    zstr_recvx (sink, &hello, &world, NULL);
    assert (streq (hello, "Hello"));
    assert (streq (world, "World"));
    zstr_free (&hello);
    zstr_free (&world);
    //  Test pause/resume functionality
    zstr_sendx (proxy, "PAUSE", NULL);
    zsock_wait (proxy);
    zstr_sendx (faucet, "Hello", "World", NULL);
    zsock_set_rcvtimeo (sink, 100);
    zstr_recvx (sink, &hello, &world, NULL);
    assert (!hello && !world);
    zstr_sendx (proxy, "RESUME", NULL);
    zsock_wait (proxy);
    zstr_recvx (sink, &hello, &world, NULL);
    assert (streq (hello, "Hello"));
    assert (streq (world, "World"));
    zstr_free (&hello);
    zstr_free (&world);
    //  Test capture functionality
    zsock_t *capture = zsock_new_pull ("inproc://capture");
    assert (capture);
    //  Switch on capturing, check that it works
    zstr_sendx (proxy, "CAPTURE", "inproc://capture", NULL);
    zsock_wait (proxy);
    zstr_sendx (faucet, "Hello", "World", NULL);
    zstr_recvx (sink, &hello, &world, NULL);
    assert (streq (hello, "Hello"));
    assert (streq (world, "World"));
    zstr_free (&hello);
    zstr_free (&world);
    zstr_recvx (capture, &hello, &world, NULL);
    assert (streq (hello, "Hello"));
    assert (streq (world, "World"));
    zstr_free (&hello);
    zstr_free (&world);
    zsock_destroy (&faucet);
    zsock_destroy (&sink);
    zsock_destroy (&capture);
    zactor_destroy (&proxy);
    //  Test socket creation dependency
    proxy = zactor_new (zproxy, NULL);
    assert (proxy);
    char *frontend = NULL;
    char *backend = NULL;
    backend = zsys_sprintf (LOCALENDPOINT, s_get_available_port ());
    zclock_sleep (200);
    sink = zsock_new_sub (backend, "whatever");
    assert (sink);
    zstr_sendx (proxy, "BACKEND", "XPUB", backend, NULL);
    zsock_wait (proxy);
    zsock_destroy(&sink);
    zactor_destroy(&proxy);
    zstr_free (&backend);
    #ifdef CZMQ_BUILD_DRAFT_API
    //  Create and configure our proxy with PUB/SUB to test subscriptions
    proxy = zactor_new (zproxy, NULL);
    assert (proxy);
    if (verbose) {
        zstr_sendx (proxy, "VERBOSE", NULL);
        zsock_wait (proxy);
    }
    zstr_sendx (proxy, "FRONTEND", "SUB", "inproc://frontend", "He", "b", NULL);
    zsock_wait (proxy);
    zstr_sendx (proxy, "BACKEND", "PUB", "inproc://backend", NULL);
    zsock_wait (proxy);
    //  Connect application sockets to proxy
    faucet = zsock_new_pub (">inproc://frontend");
    assert (faucet);
    sink = zsock_new_sub (">inproc://backend", "");
    assert (sink);
    //  Send some messages and check they arrived
    zstr_sendx (faucet, "Hello", "World", NULL);
    // since SUB is binding, subscription might be lost see:
    // https://github.com/zeromq/libzmq/issues/2267
    zsock_set_rcvtimeo (sink, 100);
    hello = zstr_recv (sink);
    if (hello) {
        assert (streq (hello, "Hello"));
        world = zstr_recv (sink);
        assert (streq (world, "World"));
        zstr_free (&hello);
        zstr_free (&world);
    }
    zsock_destroy (&faucet);
    zsock_destroy (&sink);
    zactor_destroy(&proxy);
    #endif // CZMQ_BUILD_DRAFT_API
    #if (ZMQ_VERSION_MAJOR == 4)
    // Test authentication functionality
    const char *basedirpath = "src/selftest-rw/.test_zproxy";
    const char *passfilepath = "src/selftest-rw/.test_zproxy/password-file";
    const char *certfilepath = "src/selftest-rw/.test_zproxy/mycert.txt";
    // Make sure old aborted tests do not hinder us
    zdir_t *dir = zdir_new (basedirpath, NULL);
    if (dir) {
        zdir_remove (dir, true);
        zdir_destroy (&dir);
    }
    zsys_file_delete (passfilepath);
    zsys_file_delete (certfilepath);
    zsys_dir_delete (basedirpath);
    //  Create temporary directory for test files
    zsys_dir_create (basedirpath);
    //  Check there's no authentication
    s_create_test_sockets (&proxy, &faucet, &sink, verbose);
    s_bind_test_sockets (proxy, &frontend, &backend);
    bool success = s_can_connect (&proxy, &faucet, &sink, frontend, backend,
        verbose, true);
    assert (success);
    //  Install the authenticator
    zactor_t *auth = zactor_new (zauth, NULL);
    assert (auth);
    if (verbose) {
        zstr_sendx (auth, "VERBOSE", NULL);
        zsock_wait (auth);
    }
    //  Check there's no authentication on a default NULL server
    s_bind_test_sockets (proxy, &frontend, &backend);
    success = s_can_connect (&proxy, &faucet, &sink, frontend, backend, verbose,
        true);
    assert (success);
    //  When we set a domain on the server, we switch on authentication
    //  for NULL sockets, but with no policies, the client connection
    //  will be allowed.
    zstr_sendx (proxy, "DOMAIN", "FRONTEND", "global", NULL);
    zsock_wait (proxy);
    s_bind_test_sockets (proxy, &frontend, &backend);
    success = s_can_connect (&proxy, &faucet, &sink, frontend, backend, verbose,
        true);
    assert (success);
    //  Block 127.0.0.1, connection should fail
    zstr_sendx (proxy, "DOMAIN", "FRONTEND", "global", NULL);
    zsock_wait (proxy);
    s_bind_test_sockets (proxy, &frontend, &backend);
    zstr_sendx (auth, "DENY", "127.0.0.1", NULL);
    zsock_wait (auth);
    success = s_can_connect (&proxy, &faucet, &sink, frontend, backend, verbose,
        false);
    assert (!success);
    //  Allow our address, which overrides the block list
    zstr_sendx (proxy, "DOMAIN", "FRONTEND", "global", NULL);
    zsock_wait (proxy);
    zstr_sendx (proxy, "DOMAIN", "BACKEND", "global", NULL);
    zsock_wait (proxy);
    s_bind_test_sockets (proxy, &frontend, &backend);
    zstr_sendx (auth, "ALLOW", "127.0.0.1", NULL);
    zsock_wait (auth);
    success = s_can_connect (&proxy, &faucet, &sink, frontend, backend, verbose,
        true);
    assert (success);
    //  Try PLAIN authentication
    //  Test negative case (no server-side passwords defined)
    zstr_sendx (proxy, "PLAIN", "FRONTEND", NULL);
    zsock_wait (proxy);
    zstr_sendx (proxy, "DOMAIN", "FRONTEND", "global", NULL);
    zsock_wait (proxy);
    s_bind_test_sockets (proxy, &frontend, &backend);
    zsock_set_plain_username (faucet, "admin");
    zsock_set_plain_password (faucet, "Password");
    success = s_can_connect (&proxy, &faucet, &sink, frontend, backend, verbose,
        false);
    assert (!success);
    //  Test positive case (server-side passwords defined)
    FILE *password = fopen (passfilepath, "w");
    assert (password);
    fprintf (password, "admin=Password\n");
    fclose (password);
    zstr_sendx (proxy, "PLAIN", "FRONTEND", NULL);
    zsock_wait (proxy);
    zstr_sendx (proxy, "DOMAIN", "FRONTEND", "global", NULL);
    zsock_wait (proxy);
    zstr_sendx (proxy, "PLAIN", "BACKEND", NULL);
    zsock_wait (proxy);
    zstr_sendx (proxy, "DOMAIN", "BACKEND", "global", NULL);
    zsock_wait (proxy);
    s_bind_test_sockets (proxy, &frontend, &backend);
    zsock_set_plain_username (faucet, "admin");
    zsock_set_plain_password (faucet, "Password");
    zsock_set_plain_username (sink, "admin");
    zsock_set_plain_password (sink, "Password");
    zstr_sendx (auth, "PLAIN", passfilepath, NULL);
    zsock_wait (auth);
    success = s_can_connect (&proxy, &faucet, &sink, frontend, backend, verbose,
        true);
    assert (success);
    //  Test negative case (bad client password)
    zstr_sendx (proxy, "PLAIN", "FRONTEND", NULL);
    zsock_wait (proxy);
    zstr_sendx (proxy, "DOMAIN", "FRONTEND", "global", NULL);
    zsock_wait (proxy);
    s_bind_test_sockets (proxy, &frontend, &backend);
    zsock_set_plain_username (faucet, "admin");
    zsock_set_plain_password (faucet, "Bogus");
    success = s_can_connect (&proxy, &faucet, &sink, frontend, backend, verbose,
        false);
    assert (!success);
    if (zsys_has_curve ()) {
        //  We'll create two new certificates and save the client public
        //  certificate on disk
        zcert_t *server_cert = zcert_new ();
        assert (server_cert);
        zcert_t *client_cert = zcert_new ();
        assert (client_cert);
        const char *public_key = zcert_public_txt (server_cert);
        const char *secret_key = zcert_secret_txt (server_cert);
        //  Try CURVE authentication
        //  Test without setting-up any authentication
        zstr_sendx (proxy, "CURVE", "FRONTEND", public_key, secret_key, NULL);
        zsock_wait (proxy);
        zstr_sendx (proxy, "DOMAIN", "FRONTEND", "global", NULL);
        zsock_wait (proxy);
        s_bind_test_sockets (proxy, &frontend, &backend);
        zcert_apply (client_cert, faucet);
        zsock_set_curve_serverkey (faucet, public_key);
        success = s_can_connect (&proxy, &faucet, &sink, frontend, backend,
            verbose, false);
        assert (!success);
        //  Test CURVE_ALLOW_ANY
        zstr_sendx (proxy, "CURVE", "FRONTEND", public_key, secret_key, NULL);
        zsock_wait (proxy);
        s_bind_test_sockets (proxy, &frontend, &backend);
        zcert_apply (client_cert, faucet);
        zsock_set_curve_serverkey (faucet, public_key);
        zstr_sendx (auth, "CURVE", CURVE_ALLOW_ANY, NULL);
        zsock_wait (auth);
        success = s_can_connect (&proxy, &faucet, &sink, frontend, backend,
            verbose, true);
        assert (success);
        //  Test with client certificate file in authentication folder
        zstr_sendx (proxy, "CURVE", "FRONTEND", public_key, secret_key, NULL);
        zsock_wait (proxy);
        zstr_sendx (proxy, "CURVE", "BACKEND", public_key, secret_key, NULL);
        zsock_wait (proxy);
        s_bind_test_sockets (proxy, &frontend, &backend);
        zcert_apply (client_cert, faucet);
        zsock_set_curve_serverkey (faucet, public_key);
        zcert_apply (client_cert, sink);
        zsock_set_curve_serverkey (sink, public_key);
        zcert_save_public (client_cert, certfilepath);
        zstr_sendx (auth, "CURVE", basedirpath, NULL);
        zsock_wait (auth);
        success = s_can_connect (&proxy, &faucet, &sink, frontend, backend,
            verbose, true);
        assert (success);
        zcert_destroy (&server_cert);
        zcert_destroy (&client_cert);
    }
    //  Remove the authenticator and check a normal connection works
    zactor_destroy (&auth);
    s_bind_test_sockets (proxy, &frontend, &backend);
    success = s_can_connect (&proxy, &faucet, &sink, frontend, backend, verbose,
        true);
    assert (success);
    //  Cleanup
    zsock_destroy (&faucet);
    zsock_destroy (&sink);
    zactor_destroy (&proxy);
    zstr_free (&frontend);
    zstr_free (&backend);
    //  Delete temporary directory and test files
    zsys_file_delete (passfilepath);
    zsys_file_delete (certfilepath);
    zsys_dir_delete (basedirpath);
    #endif
    #if defined (__WINDOWS__)
    zsys_shutdown();
    #endif

AUTHORS

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

RESOURCES

Main web site:

Report bugs to the email <zeromq-dev@lists.zeromq.org[1]>

COPYRIGHT

Copyright (c) the Contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for 0MQ: http://czmq.zeromq.org. 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 http://mozilla.org/MPL/2.0/. LICENSE included with the czmq distribution.

NOTES

1.  zeromq-dev@lists.zeromq.org
    mailto:zeromq-dev@lists.zeromq.org