I had the same error and impossible to find out why ... I come back on the post to send the solution if others pass here.

Simply do not initialize the replicate on both servers:

I have two separate X and Y servers without mongodb, X and Y are IP addresses or domains.

1. Install mongodb on both servers
2. Edit the sudo nano /etc/mongod.conf configuration files on both servers
3. [in file] Replace bindIp: 127.0.0.1 with bindIp: 127.0.0.1,X on the X server
4. [in file] Replace bindIp: 127.0.0.1 with bindIp: 127.0.0.1,Y on the Y server
5. [in file] Replace #replication: with replication: on both servers
6. [in file] Add replSetName: "​​myReplicatName" line under replication: on both servers
7. Launch mongo with the configuration file on both servers
8. Only on server X run mongo and type commands

Mongo commands:

rs.initiate ({
  _id: "rs0",
  members: [{
    _id: 1,
    host: "X:27017"
  }]
});
rs.add("Y:YPORT");