I am trying to write a program for file transfer using sockets. The server end of the code is running fine. However, in the client side I get the following error

Traceback (most recent call last):
File "client.py", line 54, in <module>
uploadFiles(directory)
File "client.py", line 36, in uploadFiles
transferFile(fname)
File "client.py", line 13, in transferFile     
cs.connect((HOST, 36258))
File "/usr/lib/python2.7/socket.py", line 224, in meth
return getattr(self._sock,name)(*args)
socket.error: [Errno 111] Connection refused

My code is as follows

import os
import socket

def transferFile(fname):
   HOST = '127.0.0.1'
   CPORT = 36258
   MPORT = 36250
   FILE = fname
   cs = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   cs.connect((HOST, 36258))
   cs.send("SEND " + FILE)
   cs.close()
   ms = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   ms.connect((HOST, MPORT))
   f = open(FILE, "rb")
   data = f.read()
   f.close()
   ms.send(data)
   ms.close()

def uploadFiles(directory):
   home = os.getenv("HOME")
   folder = str(home + "/" + directory)
   os.chdir(folder)
   dirList = os.listdir(folder)
   print dirList
   for fname in dirList:
       if fname.endswith('.bin'):
           transferFile(fname)

os.chdir(os.getenv("HOME"))
directory = "testdownload"
if not os.path.exists(directory):
   os.makedirs(directory)
 os.chdir(directory)

uploadFiles(directory)

I tried looking for help on Google and other posts on Stack Overflow, none of them helped. Can someone please help me?
The line numbers may be different since I pasted only some part of the code

The socket.error: [Errno 111] Connection refused error in Python occurs when a client attempts to connect to a server and the server is not available or is not listening on the specified port. This error may occur due to several reasons such as a firewall blocking the connection, incorrect IP address or port number specified, server not running, or the server being busy and unable to accept new connections.

Method 1: Check Server Availability

To fix the Python socket error “Connection refused”, we can use the “Check Server Availability” method. This method checks whether the server is available before attempting to connect to it.

Step 1: Import the necessary modules

We need to import the socket module to create a socket object and time module to add a delay between connection attempts.

import socket
import time

Step 2: Define the function to check server availability

We can define a function to check if the server is available by creating a socket object and attempting to connect to it. If the connection is successful, the server is available, and we return True. If the connection fails, we return False.

def check_server(host: str, port: int, timeout: int) -> bool:
    """
    Check if a server is available
    :param host: server hostname or IP address
    :param port: server port
    :param timeout: timeout in seconds
    :return: True if server is available, False otherwise
    """
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.settimeout(timeout)
    try:
        sock.connect((host, port))
        return True
    except socket.error:
        return False
    finally:
        sock.close()

Step 3: Use the function to connect to the server

We can use the check_server function to check if the server is available before attempting to connect to it. We can add a delay between connection attempts to avoid overwhelming the server.

host = 'example.com'
port = 80
timeout = 5

while not check_server(host, port, timeout):
    print(f"Server {host}:{port} is not available. Retrying in {timeout} seconds...")
    time.sleep(timeout)

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((host, port))

In this example, we attempt to connect to the server at example.com:80 and wait for the server to become available. Once the server is available, we connect to it using a socket object.

Method 2: Verify the IP and Port Number

To fix the Python socket error: “[Errno 111] Connection refused”, one of the solutions is to verify the IP and port number. Here are the steps to do that:

  1. First, make sure that the server is running and listening on the correct IP and port number. You can use the netstat command to check the status of the server socket.
import os

os.system("netstat -an | grep <port_number>")
  1. Check that the client is using the correct IP and port number to connect to the server. You can print the IP and port number to verify.
import socket

HOST = '<server_ip_address>'
PORT = <port_number>

print(f"Connecting to {HOST}:{PORT}")
  1. Create a socket object and try to connect to the server using the IP and port number.
import socket

HOST = '<server_ip_address>'
PORT = <port_number>

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
    s.connect((HOST, PORT))
    print("Connected successfully!")
except socket.error as err:
    print(f"Connection failed: {err}")
  1. If the connection fails, check the error message to see if it gives any hints about what went wrong. You can also try to connect to the server using a different client or tool to see if the problem is with your code or the server itself.
import socket

HOST = '<server_ip_address>'
PORT = <port_number>

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
    s.connect((HOST, PORT))
    print("Connected successfully!")
except socket.error as err:
    print(f"Connection failed: {err}")

By following these steps, you should be able to verify the IP and port number and fix the Python socket error: “[Errno 111] Connection refused”.

Method 3: Disable Firewall

To fix the Python socket error “[Errno 111] Connection refused”, you can try disabling your firewall. Here are the steps to do it:

  1. Open your firewall settings.
import subprocess
subprocess.call(["netsh", "advfirewall", "set", "allprofiles", "state", "off"])
  1. Disable the firewall.
import subprocess
subprocess.call(["netsh", "firewall", "set", "opmode", "disable"])
  1. Try connecting to the server again.
import socket

HOST = 'localhost'
PORT = 8080

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))

If the connection is successful, then the firewall was likely the issue. You can then enable your firewall again or add an exception for your Python application.

import subprocess
subprocess.call(["netsh", "advfirewall", "set", "allprofiles", "state", "on"])
import subprocess
subprocess.call(["netsh", "firewall", "set", "opmode", "enable"])

Remember to always be cautious when disabling your firewall, as it can leave your system vulnerable to attacks.

Method 4: Increase the Timeout Value

Step 1: Import the necessary modules

import socket
import time

Step 2: Set the timeout value

Step 3: Use the socket.setdefaulttimeout() method to set the timeout value

socket.setdefaulttimeout(timeout)

Step 4: Use the try-except block to catch the socket.error exception

try:
    # your socket code here
except socket.error as err:
    print("Socket error: {}".format(err))

Step 5: Add a time.sleep() method to wait for the connection

try:
    # your socket code here
except socket.error as err:
    print("Socket error: {}".format(err))
    time.sleep(timeout)

Step 6: Add a loop to retry the connection

connected = False
while not connected:
    try:
        # your socket code here
        connected = True
    except socket.error as err:
        print("Socket error: {}".format(err))
        time.sleep(timeout)

Full Example

import socket
import time

timeout = 10
socket.setdefaulttimeout(timeout)

connected = False
while not connected:
    try:
        # your socket code here
        connected = True
    except socket.error as err:
        print("Socket error: {}".format(err))
        time.sleep(timeout)

This is how you can fix the Python socket.error: [Errno 111] Connection refused error by increasing the timeout value.

Method 5: Use Telnet to Test the Connection

To fix the Python socket.error: [Errno 111] Connection refused, you can use Telnet to test the connection. Here are the steps:

  1. Open your terminal or command prompt and type the following command to start Telnet:

telnet <host> <port>

Replace <host> with the hostname or IP address of the server you want to connect to, and <port> with the port number you want to connect to.

  1. If Telnet is able to connect, you will see a message similar to this:
Trying <host>...
Connected to <host>.
Escape character is '^]'.

This means that the connection is successful.

  1. If Telnet is not able to connect, you will see a message similar to this:
Trying <host>...
telnet: connect to address <host>: Connection refused
telnet: Unable to connect to remote host

This means that the connection is not successful.

  1. To exit Telnet, type Ctrl+] followed by quit.

Here is an example Python code that uses Telnet to test the connection:

import telnetlib

HOST = '<host>'
PORT = <port>

try:
    tn = telnetlib.Telnet(HOST, PORT)
    print('Connection successful')
except ConnectionRefusedError:
    print('Connection refused')

This code tries to connect to the specified host and port using Telnet. If the connection is successful, it prints “Connection successful”. If the connection is refused, it prints “Connection refused”.

Note: Telnet is not secure and should not be used for sensitive data or passwords. Use SSH or other secure protocols instead.

Generally, in python, the connection error is not something that you will face every day, but it can sometimes happen due to various reasons. One such reason is the connection Refuse. This causes the generation of ConnectionRefusedError errno 111 connection refused message. If you are facing this error message in your coding, this might help you.

Contents

  • 1 What is socket error?
  • 2 What is ConnectionError?
  • 3 Types Of ConnectionError
  • 4 What does ConnectionRefusedError errno 111 connection refused mean?
  • 5 How to solve the ConnectionRefusedError errno 111 connection refused?
    • 5.1 Checking the connection
    • 5.2 Selectively restrict the listening socket
    • 5.3 Proper guidance to get an IP address
  • 6 FAQ
    • 6.1 How do you fix a socket error?
    • 6.2 What is the socket address in computer networks?
  • 7 Conclusion
  • 8 References

What is socket error?

A socket programming in python is used to form a bidirectional communications channel. It is generally a process of making the two unrelated network nodes communicate with each other by making a connection. This connection can be made if you know the IP address of the server.

What is ConnectionError?

Whether you are someone new to the python language or not, you must be aware of the term connection error. As suggested by the name, it is a class of exception errors related to the errors generated due to issues in the connection. It is a type of socket error that is observed in many other libraries and platforms.

In python, the ConnectionError is generally referred to as an error generated by the failure in any of the internal connections that are the connection between the application and the DBMS server mediating a peer. This type of error can be caused by various failures, such as local errors caused by the errors reported directly to the user interface programs, then local and remote errors caused while trying to connect from the local communication server to the remote communication server and the server installation. These ConnectionErrors also report directly to the applications.

Types Of ConnectionError

There are mainly three subclasses of ConnectionError such as ConnectionAbortedError, ConnectionResetError, and ConnectionRefusedError. These errors generally arise when the error is raised due to the attempt the interruption in connection with the actions of peers.

The ConnectionRefusedError errno 111 connection refused is a subclass of the ConnectionError which is caused when the peer refuses the attempts for the connection between the application and the server. This type of error corresponds to errno ECONNREFUSED messages.

The ConnectionRefusedError errno 111 connection refused is generated when the initial SYN packet to the host to be connected was responded with an RST packet instead of a SYN+ACK packet. This resulted in the declination of the program on the remote computer that needed to be connected.

This type of error can cause by many libraries and computing platforms, but the solutions to this problem are similar.

The generation of the error can be understood efficiently by using an example:

As the connection has to be made from both end so it is done in two parts:

The Server script:

connectionrefusederror errno 111 connection refused

The client script:

connectionrefusederror errno 111 connection refused

These codes might seem good, but this will result in the socket.error: [Errno 111] Connection refused message.

How to solve the ConnectionRefusedError errno 111 connection refused?

As this is a connection-based error, so the errors have to be checked on both ends that is, on the client and the server end. The ConnectionRefusedError errno 111 connection refused can be resolved using one of the following reasons.

Checking the connection

  • Ensure the IP address is of the client, and both servers are on the same LAN. If the servers are not on the same router or firewall, then you may face traffic blocking.
  • Make sure that the port is listening to the server and if not then try “netstat -ntulp”.
  • Make sure that you are accepting the connections to the server.
  • Make sure you have access to the port server of the client.

Selectively restrict the listening socket

In the example for the generation of the ConnectionRefusedError by the server you can see that there is a line as follows:

host = socket.gethostname() #Get the local machine name
port = 98406 # Reserve a port for your service
s.bind((host,port)) #Bind to the port

Instead of the above code, you can try:

port = 98406 # Reserve a port for your service
s.bind(('', port)) #Bind to the port

This way, the listening socket will not be too restricted and will ensure the connection precisely on both ends.

Proper guidance to get an IP address

To avoid ConnectionRefusedError errno 111 connection refused while coding you need to make sure to get the right IP address for that you have to put the hostname and port number for the receiver end correctly.

Due to DNS resolution, the hostname might not get translated into the local address and returned properly. So instead of the usual code:

host = socket.gethostname() #Get the local machine name
port = 98406 # Reserve a port for your service
s.bind((host,port)) #Bind to the port

You can try the code below.

host = socket.gethostbyname("localhost")
s.connect((host, port))

FAQ

How do you fix a socket error?

As the ConnectionRefusedError errno 111 connection refused is a type of socket error, resolving this may help in resolving the former error.

  • This error can be fixed by specifying the port number for which you can use the following code:
m SimpleHTTPServer (Port Number)
  • You can also free up the port by terminating the previous programs.

What is the socket address in computer networks?

The socket address is a crucial part of establishing the connection. It is generally a combination of two identifiers, that is both IP address and port number. It is defined in a header where it is specified by a data structure.

Conclusion

The ConnectionRefusedError errno 111 connection refused is a socket error that results when there is a failure in the establishment of connection when the connection is refused. Which can later be resolved by managing the data necessary for establishing the connection.

References

  1. Dizzy coding
  2. GeeksforGeeks socket programming

To learn more about some common errors follow python clear’s errors section.

Ubuntu 13

In the world of Python programming, it’s not uncommon to encounter errors and exceptions. One such error is the “ConnectionRefusedError: [Errno 111] Connection refused” which is often encountered when working with Python sockets. This error indicates that your connection request was rejected by the server or remote host. In this article, we will explore the causes of this error and how to fix it.

To fix the “ConnectionRefusedError: [Errno 111] Connection refused” error in Python sockets, you need to verify that the IP address and port number specified in your code are correct and accessible. Additionally, check your firewall settings and network configurations to ensure that there are no rules or configurations blocking the connection. Finally, make sure that the server is actively listening for connections on the specified IP address and port.

  1. Understanding Python Sockets
  2. Causes of the “ConnectionRefusedError: [Errno 111] Connection refused” Error
  3. How to Fix the Error
    • Verify the IP Address and Port Number
    • Check Firewall Settings and Network Configurations
    • Ensure the Server is Listening
  4. Conclusion

Understanding Python Sockets

Before we delve into the error, it’s important to understand what Python Sockets are. Python’s socket module provides an interface to the BSD socket system calls and library routines for network communication. It allows for the creation of client-server applications and is particularly useful in scenarios where communication is required between Python programs running on different machines in a network.

Causes of the “ConnectionRefusedError: [Errno 111] Connection refused” Error

This error typically occurs due to one or more of the following reasons:

  1. Incorrect IP Address or Port Number: If the IP address or port number specified in your code is incorrect or unreachable, the connection request will be refused.
  2. Firewall Rules or Network Configurations: Connection requests can also be blocked by firewall rules or network configurations that prevent communication between the client and server.
  3. Server is not Listening: The error can occur if the server is not actively listening for connections on the specified IP address and port.

How to Fix the Error

Now that we understand the potential causes of the error, let’s discuss how to fix it.

Verify the IP Address and Port Number

Firstly, ensure that the IP address and port number specified in your Python code are correct and accessible. Here’s an example of how to create a socket and specify the IP address and port number:

import socket

s = socket.socket()
host = 'localhost' # IP address
port = 12345 # Port number

s.connect((host, port))

In this code, socket.socket() is used to create a socket object. The connect() method is then used to establish a connection with the server. The IP address and port number are passed as a tuple to this method.

Check Firewall Settings and Network Configurations

If the IP address and port number are correct, the next step is to check your firewall settings and network configurations. Ensure that there are no rules or configurations that are blocking the connection. This process will vary depending on your operating system and network setup, so refer to the appropriate documentation or IT support for guidance.

Ensure the Server is Listening

Finally, ensure that the server is actively listening for connections on the specified IP address and port. Here’s an example of how to set up a server to listen for connections:

import socket

s = socket.socket()
host = 'localhost' # IP address
port = 12345 # Port number

s.bind((host, port))
s.listen(5) # Listen for client connection

while True:
 c, addr = s.accept() # Establish connection with client
 print('Got connection from', addr)

In this code, socket.socket() is used to create a socket object. The bind() method is then used to bind the socket to the specified IP address and port number. The listen() method is used to set the socket to listening mode and accept() is used to wait until a client connects to the server.

Conclusion

In conclusion, the “ConnectionRefusedError: [Errno 111] Connection refused” error in Python sockets can be fixed by ensuring that the IP address and port number are correct, checking firewall settings and network configurations, and ensuring that the server is actively listening for connections. By understanding these aspects and following the suggested solutions, you should be able to resolve this error effectively.

  1. Why the ConnectionRefusedError: [Errno 111] Connection refused Occurs in Python
  2. How to Solve the ConnectionRefusedError: [Errno 111] Connection refused in Python
  3. Conclusion

ConnectionRefusedError: [Errno 111] Connection Refused

This error indicates that the client cannot connect to the port on the server script’s system. Since you can ping the server, it should not be the case.

This might be caused by many reasons, such as improper routing to the destination. The second possibility is that you have a firewall between your client and server, which may be either on the server or the client.

There shouldn’t be any routers or firewalls that may stop the communication since, based on your network addresses, both the server and the client should be on the same Local Area Network.

Why the ConnectionRefusedError: [Errno 111] Connection refused Occurs in Python

This error arises when the client cannot access the server because of an invalid IP or port or if the address is not unique and used by another server.

The connection refused error also arises when the server is not running, so the client cannot access the server as the server should accept the connection first.

Code example:

# server code
import socket

s = socket.socket()
host = socket.gethostname()
port = 1717
s.bind((host, port))

s.listen(5)
while True:
    c,addr = s.accept()
    print("Got connection ", addr)
    c.send("Meeting is at 10am")
    c.close()
# client code
import socket

s = socket.socket()
host = '192.168.1.2'
port = 1717

s.connect((host,port))
print(s.recv(1024))
s.close

Output:

socket.error: [Errno 111] Connection refused

How to Solve the ConnectionRefusedError: [Errno 111] Connection refused in Python

Try to keep the receiving socket as accessible as possible. Perhaps accessibility would only take place on one interface, which would not impact the Local Area Network.

On the other hand, one case can be that it exclusively listens to the address 127.0.0.1, making connections from other hosts impossible.

Code example:

import socket

s = socket.socket()
host = socket.gethostname()
port = 1717
s.bind(('', port))

s.listen(5)
while True:
    c,addr = s.accept()
    print("Got connection ", addr)
    c.send("The Meeting is at 10 am")
    c.close()
import socket

s = socket.socket()
host = socket.gethostname()
port = 1717
s.bind(('', port))

s.connect((host, port))
print(s.recv(1024))
s.close()

Output:

Got connection('192.168.1.2')
The meeting is at 10 am

When you run the command python server.py, you will receive the message Got connection. At the same time when you run the command python client.py, you will receive a message from the server.

The DNS resolution can be the other reason behind this problem. Since the socket.gethostname() returns the hostname, an error will be returned if the operating system cannot translate it to a local address.

The Linux operating system can edit the host file by adding one line.

host = socket.gethostname()
port = 1717
s.bind((host,port))

Use gethostbyname

host = socket.gethostbyname("192.168.1.2")
s.bind((host, port))

Thus, you must use the identical technique on the client and server sides to access the host. For instance, you would apply the procedure described above in a client’s case.

You can also access through local hostname hostnamehost = socket.gethostname() or specific name for local host host = socket.gethostbyname("localhost").

host = socket.gethostname()
s.connect((host, port))
host = socket.gethostbyname("localhost")
s.connect((host, port))

Conclusion

ConnectionRefusedError in Python arises when the client cannot connect to the server. Several reasons include the client not knowing the IP or port address and the server not running when the client wants to connect.

There are several methods mentioned above to resolve this connection issue.

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