cannot assign requested address http

Cannot assign requested address [SOLVED]

April 30, 2024

The "Cannot Assign Requested Address" error is quiet common in the network community and can be seen in various network-related and application specific contexts. Here are some of the common areas where this error is seen more often:

• Nginx : When Nginx tries to bind to an IP address not present on the server, or if the port is already in use.
• Apache : Similar to Nginx, trying to bind to an unavailable IP or a busy port.
• Redis : Occurs when Redis is configured to bind to a specific IP that isn’t available.
• MySQL : If MySQL is set up to listen on an IP not assigned to the server.
• SSH : Attempting to bind to an IP address for listening or forwarding ports that isn’t available.
• FTP Servers : Similar issues when they are set to bind to specific IPs or ports.
• BIND : The DNS server attempting to bind to an IP address that does not exist on the local machine.
• Postfix : When trying to bind to a non-existent IP address for receiving or sending emails .
• OpenVPN : Trying to use an IP address for the VPN server that isn’t configured on the server.
• Docker : When a Docker container tries to bind to an IP not available on the host machine.
• Kubernetes : Similar issues when pods/services are configured with specific IPs.
• Local development servers (like those started by web frameworks such as Django or Flask ) trying to bind to an IP address that the development machine does not have configured.
• Game servers (like Minecraft, Counter-Strike) that are set to bind to a specific IP address or port which might be restricted or already in use.
• Applications that try to bind to a port for incoming connections which might already be in use or blocked by a firewall.

In this tutorial we will try to cover most of these areas and cover the cause of getting " Cannot Assign Requested Address " error and how to solve the same in individual application:

Troubleshooting "cannot assign requested address" Error

1. validate configuration.

The "cannot assign requested address" error often occurs if application is configured to bind to an IP address that isn't assigned to any network interface on the server. You need to check the configuration file based on your application:

• Nginx : Typically found at /etc/nginx/nginx.conf and /etc/nginx/conf.d/*.conf for additional server block configurations. Look out for listen directive for IP and port settings.
• Apache : Commonly located at /etc/httpd/conf/httpd.conf for CentOS/RHEL or /etc/apache2/apache2.conf and /etc/apache2/ports.conf for Debian/Ubuntu systems. Look out for Listen for IP and port configurations.
• Redis : Usually /etc/redis/redis.conf . Look out for bind and port .
• MySQL : Typically /etc/my.cnf , /etc/mysql/my.cnf , or contained within /etc/mysql/mysql.conf.d/ . Look out for bind-address and port .
• SSH : Check in /etc/ssh/sshd_config and look out for ListenAddress and Port .
• FTP Servers : Depends on the software; for vsftpd it's /etc/vsftpd.conf . Look out for listen and listen_port .
• BIND : Main configuration file is /etc/named.conf or /etc/bind/named.conf . Look out for listen-on .
• Postfix : Main configuration file is /etc/postfix/main.cf . Look out for inet_interfaces and smtp_bind_address .
• OpenVPN : Configuration file usually found in /etc/openvpn/server.conf . Look out for local for IP address binding.

Consider Nginx as an example, open the Nginx configuration file (usually located at /etc/nginx/nginx.conf or under /etc/nginx/sites-available/ ) and verify the listen directive:

Make sure the IP address in the listen directive is correct and available on your server.

Check if the IP address (e.g., 192.168.1.100 ) is assigned to the server:

This command lists all IPs assigned to your server. If 192.168.1.100 is not listed, that's likely the cause of your error. If the IP address is not on your machine, either assign that IP to the server through your network settings or change the IP in the Nginx configuration to one that is available on your server.

If the listen directive in your Nginx configuration does not specify an IP address and is simply set to listen on a port across all interfaces, like this:

Restart Nginx to ensure all settings are correctly applied:

Similarly you can check your application's Listen directive to make sure it is listening on proper interface address.

2. Check for Port conflict

It is possible that the port which your application is using is already in use by some other application service. You can use tools like netstat or ss command to check for port conflicts.

For example using netstat command :

If this gives an output then it would mean that the port is already in use. Similarly you can also use ss command :

If the port is already in use then you can either stop the service which is using your application port or alternatively you can configure your application to run on a different port number.

The configuration file details are provided in previous section for different services, after making the changes you can restart your application service.

3. Troubleshoot SELinux Issues

If you suspect that SELinux is causing issues (like preventing application service from binding to a port), you can check the audit logs to see the SELinux denials:

If there are no hints in the log file then you can also plan to change the mode of SELinux temporarily (until the next reboot) using:

When SELinux is in permissive mode, it continues to log violations to its policies as it would in enforcing mode, but it does not enforce the policies—meaning it allows actions that would otherwise be blocked.

After executing the above commands the changes will be applied immediately and a reboot is not required. You can e-verify your application status to see if this fixes "cannot assign requested address" error. Once you've replicated the issue in permissive mode, you can check the SELinux logs to see what would have been blocked. These logs are typically found in /var/log/audit/audit.log . You can use tools like audit2why to analyze these logs:

This command will show you the SELinux denials that occurred, along with explanations of why each action was denied under normal enforcing mode. This information is crucial for understanding what policies need to be adjusted.

To change the SELinux mode permanently, you will need to edit the SELinux configuration file:

In this file, change the SELINUX= line to either enforcing , permissive , or disabled . For example:

After making this change, you need to reboot your system for the changes to take effect. You can also read selinux changes to be persistent for more information.

Deepak Prasad

He is the founder of GoLinuxCloud and brings over a decade of expertise in Linux, Python, Go, Laravel, DevOps, Kubernetes, Git, Shell scripting, OpenShift, AWS, Networking, and Security. With extensive experience, he excels in various domains, from development to DevOps, Networking, and Security, ensuring robust and efficient solutions for diverse projects. You can connect with him on his LinkedIn profile.

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Error "Can't assign requested address" when ssh-ing to remote server

On ubuntu 14.04 I have installed openssh, changed the ssh port. I can login within LAN with no problems, but I cannot access it from outside.

I also have: allowed it though firewall and set up port forwarding on my linksys router

Whenever I login, I get the error (I have replaced # instead of numbers):

What else can I check, what could be wrong? Please help.

This might not fix your issue but I had the same error on OSX after it working successfully before. Flushing the routing table helped:

I ran these on the computer that I was connecting from. Reference: http://codefromabove.com/quickies/osx-cant-assign-requested-address-code49/

• 3 Hello ! Can you explain us why we have to flush the route ?? thank's –  I'm_ADR Dec 19, 2016 at 14:03
• 2 @I'm_ADR because your routing table gets corrupted from time to time. There are different reasons for it but one might be using OpenVPN on poor networks. –  Saba Ahang Nov 13, 2018 at 14:49

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How I fixed Python OSError: [Errno 99] Cannot assign requested address

When binding a socket, you see an error message like

In my case, the issue was that I was trying to bind the specific IP address  192.168.1.100 but the computer running the script did not have said IP address configured on any interface.

so I needed to change the bind IP address to either  0.0.0.0 to listen to ANY IP address or I needed to change  192.168.1.100 to the IP address of the host computer I am running the script on.

Docker container [Errno 99] Cannot assign requested address

Note that for Docker containers, either you need to run them in network_mode: host to use the host’s network systemd, or you need to bind to the container’s IP address. You can not bind to the host’s IP address from the contaienr unless using  network_mode: host ! But you can forward the ports from the host, binding to a specific IP address.

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Cannot assign requested address #856

cpiock commented Apr 12, 2019 • edited by raman-m

tomhobson commented Apr 12, 2019 • edited

Sorry, something went wrong.

cpiock commented Apr 29, 2019

Tomhobson commented apr 29, 2019.

markosmilja commented May 13, 2019

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Andrew Lock | .NET Escapades Andrew Lock

• ASP.NET Core

Why isn't my ASP.NET Core app in Docker working?

In this post I describe a problem I ran into the other day that had me stumped briefly—why doesn't my ASP.NET Core app running in Docker respond when I try and navigate to it? The problem was related to how ASP.NET Core binds to ports by default.

Background: testing ASP.NET Core on CentOS

I ran into my problem the other day while responding to an issue report related to CentOS. In order to diagnose the issue, I needed to run an ASP.NET Core application on CentOS. Unfortunately, while ASP.NET Core supports CentOS , they don't provide Docker images with it preinstalled. Currently, they provide Linux Docker images based on:

Additionally, while you can install CentOS in WSL , it's a lot more hassle than something like Ubuntu, which you can install directly from the Microsoft Store.

This left me with one obvious answer - build my own CentOS Docker image, and install ASP.NET Core in it "manually".

Creating the sample app with a Dockerfile.

I started by creating a sample web application using Visual Studio. I could have used the CLI to create the app, but I decided to use Visual Studio as I knew it would give me the option to auto-generate the Dockerfile as well. This would save a few minutes.

I chose ASP.NET Core Web API, used minimal APIs, disabled https, enabled Docker support (Linux) and generated the solution:

This generates a Debian-based dockerfile by default (the mcr.microsoft.com/dotnet/aspnetcore:6.0 images are Debian based unless you select different tags), which looks like this:

This Dockerfile uses the best practice of multi-staged builds to ensure your runtime images are as small as possible. It shows 4 distinct phases

• mcr.microsoft.com/dotnet/aspnetcore:6.0 AS base . This stage defines the base image that will be used to run your application. It contains the minimal dependencies to run your application.
• mcr.microsoft.com/dotnet/sdk:6.0 AS build . This stage defines the docker image that will be used to build your application. It includes the full .NET SDK, as well as various other dependencies . This stage actually builds your application.
• FROM build AS publish . This stage is used to publish your application.
• base AS final . The final stage is what you would actually deploy to production. It is based on the base image, but with the publish assets copied in.

Multi-stage builds are always best-practice when you're deploying to Docker, but this one is more complex than it needs to be in general. It has additional stages to make it quicker for Visual Studio to develop inside Docker images too, using "fast mode" . If you're only deploying to Docker, not developing in Docker, then you can simplify this file.

Creating a CentOS-based ASP.NET Core image

For my testing, I only needed to run the application on CentOS, I didn't need to build on CentOS, so that meant I could leave the build stage as it was, building on Debian. It was only the first stage, base , that I would need to switch to a CentOS-based image.

I started by finding the instructions for how to install ASP.NET Core on CentOS . Each Linux distro is a little bit different, with some versions using package managers, others using Snap packages etc. For CentOS we can use the yum package manager .

Installing ASP.NET Core is thankfully, very simple. You need only to add the Microsoft package repository and install using YUM. Starting from the CentOS version 7 Docker image, we can build out ASP.NET Core Docker image:

With that change to the base image, we can now build and run our sample ASP.NET Core app on CentOS using a command like the following:

Which, when you run it and navigate to http://localhost:8000/weatherforecast, looks something like this:

Debugging why the app isn't responding

I hadn't expected that result. I thought that it would be a simple case of installing ASP.NET Core, and the app would just work. My first thought was that I had introduced a bug somewhere that was causing the app to fail to start, but the logs printed to the console suggested the app was listening:

Additionally, I could see that the app was also listening on the correct port, port 5000. In my Docker command I specified that Docker should map port 5000 inside the container to port 8000 outside the container, so that also looked correct.

I double checked the documentation at this point, to make sure I had the 8000:5000 the correct way around, and yes, the format is host:container

This all seemed rather odd. Presumably , the application wasn't receiving the request at all, but just to be sure, I bumped up the logging to Debug level and tried again:

Sure enough, the logs were more verbose, but there was no indication of a request making it through

So at this point I had two possible scenarios

• The app isn't working at all
• The app isn't correctly exposed outside of the container

To test the first case I decided to exec into the container and curl the endpoint while it was running. This would tell me whether the app was running correctly inside the container, at the port I expected. I could have used the cli to do this using docker exec ... , but for simplicity I used Docker Desktop to open a command prompt inside the container , and to curl the endpoint:

Sure enough, curl -ing the endpoint inside the container (using the container port, 5000 ) returned the data I expected. So the app was working and it was responding on the correct port. That narrowed down the possible failures modes.

At this point I was running out of options. Luckily, a word in the application logs suddenly caught my eye and pointed me in the right direction. Loopback .

ASP.NET Core URLs: loopback vs. IP Address

One of the most popular posts on my blog (two years after I wrote it) is "5 ways to set the URLs for an ASP.NET Core app" . In that post I describe some of the ways you can control which URL ASP.NET Core binds to on startup, but the relevant section right now is titled "What URLs can you use?" . This section mentions that there are essentially 3 types of URLs that you can bind:

• The "loopback" hostname for IPv4 and IPv6 (e.g. http://localhost:5000 ), in the format: {scheme}://{loopbackAddress}:{port}
• A specific IP address available on your machine (e.g. http://192.168.8.31:5005 ), in the format {scheme}://{IPAddress}:{port}
• "Any" IP address for a given port (e.g. http://*:6264 ), in the format {scheme}://*:{port}

The "loopback" address is the network address that refers to "the current machine". So if you access http://localhost:5000 , you're trying to access port 5000 on the current machine. This is typically what you want when you're developing, and this is the default URL that ASP.NET Core apps bind to. So when you run an ASP.NET Core app locally, and navigate to http://localhost:5000 in your browser, everything works, because everything is all coming from the same network interface, on the same machine.

However, when you're inside a Docker container requests aren't coming from the same network interface . Essentially, you can think of the Docker container as a separate machine. Binding to localhost inside the Docker container will mean your app is never exposed outside of the container, rendering it rather useless.

The way to fix this is to ensure your app binds to any IP Address, using the {scheme}://*:{port} syntax.

As noted in my previous post , you don't have to use * in this pattern, you can use anything that's not an IP address or localhost , so you can use http://*:5000 , http://+:5000 , or http://example.com:5000 etc. All of these behave identically.

By binding the ASP.NET Core application to any IP address, the request "makes it through" from the host, so it can be handled by your app. We can set the URL at runtime when we run the Docker image, using for example

or we could bake it into the Dockerfile as shown below. The following is the complete final Dockerfile I used:

With this change we can re-build the Docker image, and run the app again with

and finally, we can call the endpoint from our browser:

So the important take away here is:

When you build your own ASP.NET Core Docker images, make sure to configure the app to bind to any IP address, not just localhost .

Of course, the official .NET Docker Images do that already , binding to port 80 by setting ASPNETCORE_URLS=http://+:80 .

In this post I described a situation in which I was trying to build a CentOS Docker image to run ASP.NET Core. I described how I created the image by following the ASP.NET Core installation instructions, but that my ASP.NET Core app wasn't responding to requests. I walked through my debugging process to try to get to the root cause of the problem, and realised that I was binding to the loopback address. This meant the application was accessible from inside the Docker container, but not from outside it. To resolve the issue, I made sure to bind my ASP.NET Core app to any IP address, not just localhost .

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bind: cannot assign requested address

I've recently switch over to AWS from Rackspace and I'm setting up a simple geolocation server using freegeopip . While the following commands work perfectly on a new Rackspace serve (Ubuntu) I can't getting working on AWS (tried Red Hat and Ubuntu). Here is the code I've used to set it up:

As I've said this works perfecectly on my Rackspace instace but AWS gives me this error:

I've checked this port with netstat and there is nothing running on it. I have no idea why I'm getting this error. Any ideas?

• amazon-web-services
• geolocation

2 Answers 2

In many cases, binding to 0.0.0.0 is the best course of action unless you have a specific reason to bind only to a specific address.

But I assume that what you're doing isn't working, because you're trying to bind to the instance's public IP address, which you'll find (via ifconfig ) your IP stack isn't aware of.

AWS instances are only natively aware of their private IP address, which is what you need to bind to.

EC2 (classic and VPC) instance public addresses associates with instances are 1:1 NAT translated to the private address by the AWS network infrastructure.

• I am also facing same issue.I want to use public ip of openstack vm instead of private ip i.e. eth0 ip. –  Vikram Ranabhatt Mar 27, 2016 at 11:50
• @Chris_vr this question is about AWS, where binding to the wildcard or private IP specifically is the correct (and only) option. Openstack, I have no idea, but if you only see the private IP bound to the stack, the answer is probably similar, and if so, then trying to bind a socket to the public IP is the wrong way to accomplish what you are trying to do. –  Michael - sqlbot Mar 27, 2016 at 11:59

AWS runs network address translation between your instance and the internet. So, the AWS instance might be reachable by the IP address 08.08.08.0808, however the server is actually configured to use 88.88.88.88. What I need to do was bind to the internal IP of the server which I found with ifconfig.

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