SSH tunneling and example Python client-server codes
This document demonstrates how we could run client-server software via SSH. The main purpose of using this technique relies on that on most HPC servers most of the IP ports are nromally blocked except for the SSH port 22.
- SSH tunneling settings in PuTTY
In this case, the server port 8888 is mapped to the local port 7777. The meaing of this is simple: once connected to the server using PuTTY, any data on the server sent/received at port 8888 will be redirect to the port 7777 of the local machine (the computer you are using PuTTY at the moment). As a result, any client software running on the client computer can communicate with the server program via the local port 7777.
- Example Python client-server codes using SSHUsage: SSH to the server using PuTTY (with the tunneling settings in Step 1); execute the server code on the server; then run the client code on the local computer.The server code:
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#!/usr/bin/python
import sys
from socket import *
myHost = '10.72.1.1' #the server IP
myPort = 8888 #the server port
s = socket(AF_INET, SOCK_STREAM) # create a TCP socket
s.bind((myHost, myPort)) # bind it to the server port
s.listen(5) # allow 5 simultaneous
# pending connections
print "Send 'close' to server to terminate the connection"
print "Waiting for incoming connection ..."
while 1:
# wait for next client to connect
connection, address = s.accept() # connection is a new socket
while 1:
data = connection.recv(1024) # receive up to 1K bytes
if data:
print "Data from client %s: %s" % (address,data)
if data=="close":
#connection.close()
print "Disconnected with ", address
#sys.exit()
break
#print connection, address
connection.send('server feedback -> ' + data)
else:
break
connection.close() # close socket
print "Server closed."The client code:
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17import sys
from socket import *
serverHost = '127.0.0.1' # localhost
serverPort = 7777 # local port for SSH tunneling
s = socket(AF_INET, SOCK_STREAM) # create a TCP socket
s.connect((serverHost, serverPort)) # connect to server on the port
s.send('Hello world') # send the data
data = s.recv(1024) # receive up to 1K bytes
print dataShare this:
