<img src="/img/2015/09/zeromq_logo.png" alt="zeromq_logo"> When getting started on ZeroMQ (version 4.2.0 or above) can be quite challenging especially with all the prerequisites. I’ve spent a good two days to get the process ironed out. So I’m sharing this so that others can avoid the same pitfalls and can have a good head-start with setting up their environment.

Pitfall #1: Develop for your platform. I’m accustomed to developing in Ubuntu 14.04.3 LTE but in this case my deployment environment happens to be CentOS 6.7 (minimal server). Because the dependencies such as GLIBC versions are different, it’s best to stick to a setup with the target platform in mind.

This exercise assumes that you’ve installed CentOS 6.7 (minimal server option).

Pitfall #2:

In your research you may have come across the following errors below. I’m including them in hopes that the search engine bots will bring you to this blog so that you can save some headaches.

[sourcecode language=“jscript”] checking whether the C compiler works… configure: error: in /root/downloads/libzmq-master’: configure: error: cannot run C compiled programs. If you meant to cross compile, use –host’. [/sourcecode]

[sourcecode language=“jscript”] libsodium is not installed [/sourcecode]

[sourcecode language=“jscript”] src/.libs/libzmq.so: undefined reference to crypto_secretbox_open' src/.libs/libzmq.so: undefined reference to crypto_box_beforenm' src/.libs/libzmq.so: undefined reference to crypto_secretbox' src/.libs/libzmq.so: undefined reference to crypto_box' src/.libs/libzmq.so: undefined reference to crypto_box_keypair' src/.libs/libzmq.so: undefined reference to sodium_init' src/.libs/libzmq.so: undefined reference to crypto_box_open' src/.libs/libzmq.so: undefined reference to randombytes_close' src/.libs/libzmq.so: undefined reference to crypto_box_open_afternm' src/.libs/libzmq.so: undefined reference to randombytes' src/.libs/libzmq.so: undefined reference to crypto_box_afternm' collect2: ld returned 1 exit status make[1]: *** [tools/curve_keygen] Error 1 make[1]: Leaving directory /root/downloads/libzmq-master' make: *** [all-recursive] Error 1 [/sourcecode]

[sourcecode language=“jscript”] GLIB 2.14 not found [/sourcecode]

Solution:

The following steps provides you a step-by-step instruction to get you to a point where you can compile the standard ZeroMQ HelloWorld Server and HelloWorld Client.

[sourcecode language=“jscript”]

Steps to a working ZeroMQ 4+ code on CentOS67

Login as root or make sure you have sudo access

The following instructions assume you are logged in as “root”

Assumes the following path /root/downloads

mkdir download cd download

ZeroMQ 4+ requires libsodium

You also need a C compiler

Pre-requisites

yum update

Gets your system upto date with the latest updates

yum install libtool gcc-c++ glib*

This installs autoconf, automake, cloog-ppl, cpp, gcc, mpfr, ppl

yum groupinstall “development tools”

Let us install and build libsodium

wget https://download.libsodium.org/libsodium/releases/libsodium-1.0.3.tar.gz tar -xvf libsodium-1.0.3.tar.gz cd libsodium-1.0.3 ./configure make clean make make install

libsodium libraries are now installed under /usr/local/lib directory

Next we need to tell libzmq and other development code where to find these libraries

Add the following exports defining the following environmental libraries

Edit the root users .bashrc file

vim /root/.bashrc

Add the following

#—– export sodium_CFLAGS="-I/usr/local/include" export sodium_LIBS="-L/usr/local/lib" export CPATH=/usr/local/include export LIBRARY_PATH=/usr/local/lib export LD_LIBRARY_PATH=/usr/local/lib export LD_RUN_PATH=/usr/local/lib export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig export CFLAGS=$(pkg-config –cflags libsodium) export LDFLAGS=$(pkg-config –libs libsodium) #—–

Reinitialize settings under .bashrc

source ~/.bashrc

Add libsodium to ldconfig

echo ‘/usr/local/lib’ > tee -a /etc/ld.so.conf.d/libsodium.conf

Download the latest lizmq from the GIT repository

cd /root/downloads wget https://github.com/zeromq/libzmq/archive/master.zip unzip master.zip cd libzmq-master

Lets begin building it

Generate the configure script from template

./autogen.sh ./configure make clean make make install

ZeroMQ libraries are installed in /usr/local/lib path

Need to add the libraries to ldconfig so that they can be

statically linked in C code

Since ZMQ is installed in the same path as libsodium,

we do not need to add another path into /etc/ld.so.conf.d/*.conf

we just need to reload the “ldconfig”

ldconfig

Let try compiling and testing a sample code

mkdir /root/downloads/zmqtest cd /root/downloads/zmqtest

vim helloserver.c

Copy hwserver code from the following url:

wget https://github.com/imatix/zguide/raw/master/examples/C/hwserver.c

Copy hwclient code from the following url:

wget https://github.com/imatix/zguide/raw/master/examples/C/hwclient.c

Compile hwserver

gcc hwserver.c -o hwserver -lzmq gcc hwclient.c -o hwclient -lzmq

Open two SSH terminals to /root/downloads/zmqtest

Run hello-world server in terminal #1

Run hello-world client in terminal #2

If it runs, you’re all set to go

Please link me from your blog/social places so that others can easily find this article

Also provide me with feedback so that I can ammend this guide for others

[/sourcecode]

Thank you & cheers!