I have learn basic zookeeper concept and did a sample project, But I only it only local pc or one computer.
I understand the zookeeper but still confused on how the client connect to the zookeeper server if they are not in one computer? for instance, if we start a zookeeper server in my own computer, and we can use connect() like connect 2181 to connect to the zookeeper server, that make sense, since they are all in one computer have have some association in lower layer. But what if the zookeeper server and client they are separated into two computer? how can we handle that?
I'm not sure what language you're using for the client, so this will have to be a generic answer.
The client and server communicate over TCP. This requires that the client simply know the server's host and port. In general, your ZooKeeper servers bind to some private network interface. For instance, your zoo.conf configuration file might contain a line like the following:
clientPort=2181
server.1=123.456.789.1:2888:3888
The first portion of the server.1 section 123.456.789.1 is the host to which the ZooKeeper server will bind. As long as this host is not the loop back interface (i.e. localhost or 127.0.0.1) you should be able to connect to that host from another machine on the client port 2181. So, for instance, in Java I create a new ZkClient that points to that host and port:
ZkClient client = new ZkClient("123.456.789.1:2181");
Related
I have set up a client and a server using sockets in python where my client sends data to the server, servers performs an operation, then returns some data to the client. Originally both the client and server were to have the same port number (9999). My issue currently is that I have to change the port of the server to 19999, and when I try to run, it does not work. The client is able to send data if its port is also changed to 19999, but it does not work if client is 9999 and server is 19999, which is what I need. New to networking systems so would appreciate any useful links to information or advice.
pic of client (left) and server (right)
Normally, clients will use an ephemeral port for its local port, and connect to the server port. Your client code is attempting to connect to port 9999, which is not the server port, which explains why it is not working. You need to connect to port 19999, since that is the port the server is listening on.
Using an unbound socket causes the client to choose an ephemeral port for its local address when making a connection. If you want the client to bind to a specific port, use bind before you call connect.
# bind locally to 9999
local_addr = (host, 9999)
s.bind(local_addr)
# connect to 19999
remote_addr = (host, 19999)
s.connect(remote_addr)
I have my Kafka Server running on other system. I am trying to run the client from my local machine by giving the broker url of the machine where Kafka server is running. But unfortunately i am not able to connect to kafka server.
server.properties files has the below attributes:
group.initial.rebalance.delay.ms=0
listeners=SASL_PLAINTEXT://localhost:9093
advertised.listeners=SASL_PLAINTEXT://localhost:9093
#advertised.listeners=SASL_PLAINTEXT://10.97.123.52:9093
security.inter.broker.protocol=SASL_PLAINTEXT
sasl.mechanism.inter.broker.protocol=PLAIN
sasl.enabled.mechanisms=PLAIN
while running my client from my local machine, i am passing the broker url of the server machine, but unable to connect:( . Can anyone help in this problem?
A bit simplified, but ... the client first connects to the bootstrap server to get the metadata. A based on that metadata it will open another TCP connection to the broker which is leader for the topic/partition the clients wants to speak with.
The first connection is done based on the bootstrap server address which you set. The second connection is opened to the address from the metadata. And the metadata will in your case contain the address from the advertised.listeners field, which is localhost. So the client will try to connect to localhost:9093 and not to your broker. So you need to set the advertised.listeners to use the address under which the broker is visible for the clients. (which is maybe the line which is commented out in your config example?)
You have also the listener field set to listen on localhost only. So it will not be accessible from the external IP address. You have to change it to listen on the external IP address. Most propbably setting it to the following value (i.e. without localhost) should help:
listeners=SASL_PLAINTEXT://:9093
Let's assume I'm in computer A, I have a few servers running on different ports, but all are basically an instance of the same program (just binding to different ports). Now, computer B, a client, does he need to know what port is the software he wishes to connect to on computer A?
The point is, I am implementing some sort of communication similar to sockets. Everything should work fine but I'm not sure how to create the initial-message from a computer to another - I just don't know to what port to send it to. Does the client know the port he's sending to on the server?
Say here (client): clientsocket.connect(('localhost', 8089)), does the client connect a server running on port 8089? If so, what port is his socket on (what port is he using for the client?
Yes. The only way for the network stack on computer A to know which process to deliver an incoming packet is for computer B to set the correct port in the packet. A web server runs on port 80 by default, but a machine running several distinct web servers will run them on distinct ports, and a client must be specific about which server they want to connect to. http://example.com, http://example.com:8080, and http://example.com:12345 would refer to the servers running on example.com on ports 80, 8080, and 12345, respectively.
In order to know which port to use in your client, you need to read the documentation for the server you want to connect to.
Going in the other direction, the port used by the client to receive responses is typically set by the networking stack automatically. The client doesn't need to do anything special to set it, and the server simply sends packets back to the address/port found in the source portion of the incoming packet.
I am not sure how to use a single port at server side simultaneously for multiple sockets. How can we do it in node.js. I am currently using socket.io and have one socket per port. In case solutions do not exist but is possible then also please give your suggestion to achieve the same. Also what issues can be there if we share a port? What could be other related options considering the situation that clients can be idle but will consume a port on server as we need to maintain a socket connection for each client?
Assuming your server is running on port 80, here is what happens underneath:
Server listens port 80.
Client1 connects to server port 80 from its port 12345
Server accepts client1's connection request and assigns port 9876 to commune with client1.
Server continues listening port 80.
So despite what you think, the port 80 is not consumed, it is a listener. Your computer probably has 50000 ports at free, so there is no problem.
FYI: Ports cannot be shared among other processes. Only Node's child processes can be shared, have a look at how it can be: http://nodejs.org/docs/latest/api/cluster.html
I have a simple node.js client and server programs running on one machine and when I try to connect to the server with second instance of client program simultaneously I get EADDRINUSE, Address already in use error. Is it possible to have two or more TCP based socket client connections (created with createConnection) to one server (created with createServer) on the same machine, or only one client program can be connected to the server at the same time?
Yes, it's possible. Infact, very common. Many applications open dozens, or hundreds of connections to the same server. It sounds like your client program is binding on a port. Only the server should be binding on a port. You should verify.
The client will usually use a random port between 1024-65535, as assigned by your OS. You don't need to worry about it. Since the client is initiating a connection to the server, the server port must unique to one program. Which is why your problem signifies you are trying to start the server twice. Please see http://www.tcpipguide.com/free/t_TCPIPClientEphemeralPortsandClientServerApplicatio.htm