[nanomsg] When is it safe to use NN_MSG?
- From: Stefan de Konink <stefan@xxxxxxxxx>
- To: <nanomsg@xxxxxxxxxxxxx>
- Date: Wed, 11 Dec 2013 03:27:55 +0100
I'm currently using a construction where an iov contains a uint32_t and a
struct. It make sense that I have to manually set iov_len with the appropriate
sizes of these objects.
When receiving the object back, I should receive a string-like object (instead
of the struct). I was expecting I could use a lazy method let nanomsg do my
allocation like in the test.
https://github.com/nanomsg/nanomsg/blob/master/tests/msg.c#L81
For some reason I cannot get the following to work, either response side
remains 0x0 or it plainly hangs.
Sender>>
void *msg = nn_allocmsg(result_length, 0);
strncpy(msg, result_buf, result_length);
iov[0].iov_base = &sd;
iov[0].iov_len = sizeof(uint32_t);
iov[1].iov_base = &msg;
iov[1].iov_len = NN_MSG;
bzero (&hdr, sizeof (hdr));
hdr.msg_iov = iov;
hdr.msg_iovlen = 2;
nn_sendmsg(sock, &hdr, 0);
<<Receiver
char *response = NULL;
uint32_t sd;
struct nn_msghdr hdr;
struct nn_iovec iov [2];
iov [0]iov_base = &sd;
iov [0].iov_len = sizeof(uint32_t);
iov [1].iov_base = &response;
iov [1].iov_len = NN_MSG;
bzero(&hdr, sizeof (hdr));
hdr.msg_iov = iov;
hdr.msg_iovlen = 2;
nn_recvmsg (broker_socket, &hdr, 0);
When I change the iov[1] parts on both sides to preallocated buffers, with a
fixed size, I do get messages around. Could someone give a hint?
Stefan#include <nanomsg/nn.h>
#include <nanomsg/reqrep.h>
#include <string.h>
#include <stdio.h>
#include <stdint.h>
int main() {
struct nn_msghdr hdr;
struct nn_iovec iov[2];
int req = nn_socket(AF_SP, NN_REQ);
int rep = nn_socket(AF_SP, NN_REP);
nn_bind(rep, "tcp://127.0.0.1:1234");
nn_connect(req, "tcp://127.0.0.1:1234");
uint32_t sd = 1;
char *result_buf = "Hello world";
int result_length = strlen(result_buf);
void *msg = nn_allocmsg(result_length, 0);
strncpy(msg, result_buf, result_length);
iov[0].iov_base = &sd;
iov[0].iov_len = sizeof(uint32_t);
iov[1].iov_base = &msg;
iov[1].iov_len = NN_MSG;
bzero (&hdr, sizeof (hdr));
hdr.msg_iov = iov;
hdr.msg_iovlen = 2;
printf("Sending...\n");
nn_sendmsg(req, &hdr, 0);
char *response = NULL;
iov [0].iov_base = &sd;
iov [0].iov_len = sizeof(uint32_t);
iov [1].iov_base = &response;
iov [1].iov_len = NN_MSG;
bzero(&hdr, sizeof (hdr));
hdr.msg_iov = iov;
hdr.msg_iovlen = 2;
printf("Receiving...\n");
nn_recvmsg (rep, &hdr, 0);
printf("Worked...\n");
nn_sendmsg(rep, &hdr, 0);
nn_recvmsg (req, &hdr, 0);
printf ("%s", response);
}
Other related posts:
