How to construct a URI with username password for mongo C driver.

I am using mongo 3.0.8. I have an authenticated user admin with password admin. I am able to connect to the mongo shell as follows.

mongo admin -u amdin -p amdin

However, i tried to connect to using the following C code. This gives me an error

WARNING: client: Failed to connect to: ipv4 127.0.0.1:27017, error: 111, Connection refused

char URI[256];
snprintf(URI,256,"mongodb://admin:admin@127.0.0.1:27017/?authSource=admin");
mongoc_client_t *client = mongoc_client_new(URI);

Solution

The error error: 111, Connection refused is a networking error. Your URI expecting to find the server listening on port 27017 of the same machine (127.0.0.1). Possible issues:

Server not running
Server not on that port
Server is bound to the "real ip address" of the machine.
There is local firewall (e.g. iptables) blocking access
Maybe an SELinux problem?

If this is a Linux box, these commands might help diagnose:

netstat -an -A inet | grep LISTEN
/sbin/iptables -L