how to get real ip address of client

I shared is a method in Java that retrieves the IP address of a client from an HttpServletRequest object. It checks various headers that may contain the client’s IP address if the request is coming through a proxy or load balancer. Here's a breakdown of how the method works:

Breakdown of the Method:

1. x-forwarded-for Header:

java

ip = request.getHeader("x-forwarded-for");

 

ü  The x-forwarded-for header is commonly used by proxies and load balancers to forward the original IP address of the client making the request.

ü  If the request is routed through a proxy, the actual client IP address will be in this header.

ü  If the header is null, empty, or has the value "unknown", it proceeds to the next step.

2. Proxy-Client-IP Header:

java

ip = request.getHeader("Proxy-Client-IP");

 

ü  This header is typically added by some proxies to indicate the original client’s IP address.

ü  The method checks this header if the x-forwarded-for header doesn’t provide a valid value.

3. WL-Proxy-Client-IP Header:

java

ip = request.getHeader("WL-Proxy-Client-IP");

 

ü  The WL-Proxy-Client-IP header is used by WebLogic servers. This is checked next if the previous headers don’t have a valid IP.

4. Fallback to request.getRemoteAddr():

java

ip = request.getRemoteAddr();

 

ü  If none of the proxy-related headers contain a valid IP, the method falls back to request.getRemoteAddr(), which provides the IP address directly from the request.

ü  This method gives the IP of the client directly connected to the server, which could be the actual client or a proxy/load balancer.

Return Value:

The method finally returns the detected IP address, whether it was found in a header or directly from the request.

Complete Code:

java

public String getIpAddr(HttpServletRequest request) {     String ip = request.getHeader("x-forwarded-for");     if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {         ip = request.getHeader("Proxy-Client-IP");     }     if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {         ip = request.getHeader("WL-Proxy-Client-IP");     }     if(ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {         ip = request.getRemoteAddr();     }     return ip; }

 

Usage Considerations:

1. Proxies and Load Balancers: If the application is behind multiple proxies, the x-forwarded-for header might contain multiple IP addresses (comma-separated), where the first one is usually the real client IP.
2. Security: Since the headers like x-forwarded-for can be manipulated by the client, it's important to not rely on them blindly in a high-security context. Make sure the proxies or load balancers you trust are the ones adding these headers.
3. IPv6 Support: This method works for both IPv4 and IPv6 addresses.

Example Usage:

You can use this method in a servlet or controller to log or handle requests based on the client's IP.

java

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {     String clientIp = getIpAddr(request);     System.out.println("Client IP: " + clientIp);     // Additional logic based on IP address }

 

To get real ip address from client request address