i'm getting following error while connecting to mongodb server - mongodb

Question

$ mongo
MongoDB shell version v3.6.3
connecting to: mongodb://127.0.0.1:27017
2018-10-18T17:09:03.003+0530 W NETWORK [thread1] Failed to connect to 127.0.0.1:27017, in(checking socket for error after poll), reason: Connection refused
2018-10-18T17:09:03.004+0530 E QUERY [thread1] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed :
connect#src/mongo/shell/mongo.js:251:13
#(connect):1:6
exception: connect failed

Answer 1

what OS are you using? In ubuntu you need to check your version:
service mongod status, mongod --version.
If mongod is off then just restart and write the error if possible.
service mongod restart

Answer 2

if you are using linux, try this command
$ sudo mongod
you are getting that because you are running
$ mongo

Answer 3

First go to your mongoDB directory and in that directory go to bin directory and open terminal in that directory(bin), then run the following command:
mongod.exe
After that open another terminal in same directory and run the following command.
mongo.exe
It will resolve this issue.

Answer 4

first you check it mongodb proper installed or not and also check it version compatibility
I am saying windows os setup,
set environment variable is path C:\Program Files\MongoDB\Server\3.6\bin;
then open your command prompt and type
mongod
after open another command prompt and type
mongo

Answer 5

A connection refused failure to connect reason may just be a matter of your network configuration and firewall or more specifically, your operating system's port restrictions. While you may be connecting to a mongoDB server on localhost (127.0.0.1) which can't be blocked by a firewall, it is possible for a firewall to block access to specific ports on a localhost.
If you're on a linux-based system, this can be addressed by using iptables as described here with the applicable commands shown below:
iptables -A INPUT -s 127.0.0.1 -p tcp --destination-port 27017 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -d 127.0.0.1 -p tcp --source-port 27017 -m state --state ESTABLISHED -j ACCEPT
However, in reading the comments on another answer, it may be that you aren't able to connect because the server isn't being launched and ran properly due to a lack of of the /data/db directory. But, a presumption based on the lack of reply to other answers suggesting to check your server is running properly, tells me you're sure that it is. In which case, try changing your hostname to localhost instead of 127.0.0.1 when connecting, as in:
mongoose.connect('mongodb://localhost:27017');
# or as more applicable for connecting to a deployment:
mongosh "mongodb://localhost:27017"
# alternatively, by default, MongoDB Shell already connects to localhost
# so you could simply use the command line option --port such as:
mongosh --port 27017
You can also try specifying more parameters in the url as it applies.
For example, connecting to an instance and authenticate against the foobar database as user rohan:
mongosh "mongodb://localhost:27017" --username rohan --authenticationDatabase foobar
To provide a password with the command instead of using the masked prompt, simply add the --password command line option.
For Windows, you may also try the solutions offered on this page.