Sending ZeroMQ data using TCP - http

Question

I am trying to make a simple server.
A language I am restricted to use is c++.
I am using ZeroMQ.
I have creatred a simple server and a client, as in documentation.
ZeroMQ uses TCP instead of HTTP.
I know that HTTP's underlying layer is TCP, so I want to know will it have any performance issues by using TCP instead of HTTP.
And for HTTP I can use curl to test the application.
What should I use for TCP ( curl command to send request to a socket with a string parameter ).
Server:
#include <zmq.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
int main (void)
{ // Socket to talk to clients
void *context = zmq_ctx_new ();
void *responder = zmq_socket (context, ZMQ_REP);
int rc = zmq_bind (responder, "tcp://*:5555");
assert (rc == 0);
while (1)
{
char buffer [10];
zmq_recv (responder, buffer, 10, 0);
printf ("Received Hello\n");
// trying to send json object
zmq_send (responder, "World", 5, 0);
// zmq_send (responder, "World", 5, 0);
sleep (1); // Do some 'work'
}
return 0;
}
client:
// Hello World client
// Connects REQ socket to tcp://localhost:5555
// Sends "Hello" to server, expects "World" back
#include <zmq.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
int main (void)
{
void *context = zmq_ctx_new ();
// Socket to talk to server
printf ("Connecting to hello world server...\n");
void *requester = zmq_socket (context, ZMQ_REQ);
zmq_connect (requester, "tcp://localhost:5555");
int request_nbr;
for (request_nbr = 0; request_nbr != 10; request_nbr++)
{
zmq_msg_t request;
zmq_msg_init_size (&request, 5);
memcpy (zmq_msg_data (&request), "Hello", 5);
printf ("Sending Hello %d...\n", request_nbr);
zmq_msg_send (&request, requester, 0);
zmq_msg_close (&request);
zmq_msg_t reply;
zmq_msg_init (&reply);
zmq_msg_recv (&reply, requester, 0);
printf ("Received World %d\n", request_nbr);
zmq_msg_close (&reply);
}
zmq_close (requester);
zmq_ctx_destroy (context);
return 0;
}

Answer 1

Q1: will it have any performance issues by using TCP instead of HTTP?
A1: yes, it will. Both performance and latency will benefit from avoiding HTTP-rich-re-wrapping of data
Q2: What should I use for TCP to send a request to a socket with a string parameter?
A2: No command ( curl command ) will help you. ZeroMQ uses certain line-code ( assume it as a trivial protocol between communicationg peers ), so a standalone command-line tool will not be able to match the line-code requirement off-the-shelf. Solution? Create a simple c-programme, that will consume a cmd-line arguments ( the string, as an example ) and assemble a ZeroMQ-layer compatible data-framing so as to communicate with the remote peer. Also you shall notice, that for ZeroMQ REQ/REP Formal Communication Pattern to work, this proxy-tool will have to become the sole respective REQ, resp. REP entity in the step-forward-locking diadic-communication relation, thus also providing an awaited response, the REQ-side is expecting to receive after the REP-side has received a message.