[zeromq-dev] ZMQ_MAX_SOCKETS ignored?

[Auer, Jens]

I think I can try to answer my own question. Thinking about it, the option probably restricts th number of zeroMQ sockets that can be created in the given context, and not the number of TCP sockets that are used in the backend. So, when I set the option to 1, I can create 1 zeroMQ socket, e.g. a PUB, but have many SUB sockets connected. Is that right?

Cheers,
  Jens

--
Jens Auer | CGI | Software-Engineer
CGI (Germany) GmbH & Co. KG
Rheinstraße 95 | 64295 Darmstadt | Germany
T: +49 6151 36860 154
jens.auer at cgi.com<mailto:jens.auer at cgi.com>
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________________________________
Von: zeromq-dev-bounces at lists.zeromq.org [zeromq-dev-bounces at lists.zeromq.org]" im Auftrag von "Auer, Jens [jens.auer at cgi.com]
Gesendet: Donnerstag, 24. September 2015 09:16
An: ZeroMQ development list
Betreff: [zeromq-dev] ZMQ_MAX_SOCKETS ignored?

Hi,

I am trying to use a context with ZMQ_MAX_SOCKETS to restrict the possible number of connections. In my example, I set ZMQ_MAX_SOCKETS to 2 and start a server with ZMQ_STREAM sockets. The client uses posix sockets to connect to the server. From what I see, it seems that the number of sockets is ignored because I can connect more than 2 clients. Am I missing something?

The server code:
#include <zmq.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
    void* ctx = zmq_ctx_new();
    int rc = zmq_ctx_set( ctx, ZMQ_MAX_SOCKETS, 2 );
    assert( rc == 0 );

    int major = 0;
    int minor = 0;
    int patch = 0;

    zmq_version(&major, &minor, &patch);
    printf("This is zeroMQ %d.%d.%d\n", major, minor, patch);

    void* s = zmq_socket(ctx, ZMQ_STREAM);
    assert(s);
    rc = zmq_bind(s, "tcp://*:10000");
    assert(rc == 0);

    uint8_t id[256];

    while(1)
    {
        printf("Waiting for client...\n");
        memset(id, 256, '\0');
        int n = zmq_recv(s, id, 256, 0);

        printf("Client connected\n");
        for(int i=0; i != n; ++i)
        {
            printf("%0x", (int)id[i]);
        }
        printf (" (%d)\n", n);

        n = zmq_recv(s, id, 256, 0);
        assert(n == 0);
    }
}

The client code:
int main()
{
    struct sockaddr_in serv_addr;
    int sockfd;
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
    {
        printf("\n Error : Could not create socket \n");
    }

    memset(&serv_addr, '0', sizeof(serv_addr));

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(10000);

    if(inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr)<=0)
    {
        printf("\n inet_pton error occured\n");
    }

    if( connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
    {
       printf("\n Error : Connect Failed \n");
    }

    int i; std::cin >> i;

    return 0;
}

Running the server, and stating four clients gives the following output:
This is zeroMQ 4.1.2
Waiting for client...
Client connected
06b8b4567 (5)
Waiting for client...
Client connected
06b8b4568 (5)
Waiting for client...
Client connected
06b8b4569 (5)
Waiting for client...
Client connected
06b8b456a (5)
Waiting for client...

Since I don't see any disconnect messages for the clients, it looks like all four clients are connected. netstat confirms this.

Best wishes,
  Jens

--
Jens Auer | CGI | Software-Engineer
CGI (Germany) GmbH & Co. KG
Rheinstraße 95 | 64295 Darmstadt | Germany
T: +49 6151 36860 154
jens.auer at cgi.com<mailto:jens.auer at cgi.com>
Unsere Pflichtangaben gemäß § 35a GmbHG / §§ 161, 125a HGB finden Sie unter de.cgi.com/pflichtangaben<http://de.cgi.com/pflichtangaben>.

CONFIDENTIALITY NOTICE: Proprietary/Confidential information belonging to CGI Group Inc. and its affiliates may be contained in this message. If you are not a recipient indicated or intended in this message (or responsible for delivery of this message to such person), or you think for any reason that this message may have been addressed to you in error, you may not use or copy or deliver this message to anyone else. In such case, you should destroy this message and are asked to notify the sender by reply e-mail.
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