How to clear socket buffer in linux?

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#include <sys/types.h>
#include <sys/socket.h>

int main() {
    int sockfd = /* your socket file descriptor */;
    
    int bufsize = 0;
    socklen_t optlen = sizeof(bufsize);
    
    // Get the current receive buffer size
    if (getsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &bufsize, &optlen) == -1) {
        perror("getsockopt");
        return 1;
    }
    
    printf("Current receive buffer size: %d
", bufsize);
    
    // Set the receive buffer size to zero
    bufsize = 0;
    if (setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &bufsize, optlen) == -1) {
        perror("setsockopt");
        return 1;
    }
    
    // Get the receive buffer size again to verify that it has been cleared
    if (getsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &bufsize, &optlen) == -1) {
        perror("getsockopt");
        return 1;
    }
    
    printf("Updated receive buffer size: %d
", bufsize);
    
    return 0;
}