unsigned conversion 'int' to 'unsigned char'

 The following class represent an IPv4 address. This is a 32-bit value, usually represented in decimal dotted format, such as 192.168.1.100, each part of it is an 8-bit value, ranging from 0 to 255. For easy representation we can use four unsigned char to store address. The following listing whos a minimal implementation that can meet the above description.

#include <array>
#include <string>
#include <sstream>
#include <iostream>

using namespace std;

class ipv4
{
    array<unsigned char, 4> data;

public:
    constexpr ipv4() : data{ {0} } {}
    constexpr ipv4(unsigned char const a, unsigned char const b,
                   unsigned char const c, unsigned char const d):
        data{{a, b, c, d}} {}

    explicit constexpr ipv4(unsigned long a) :
        data{ { static_cast<unsigned char>((a >> 24) & 0xFF),
                static_cast<unsigned char>((a >> 16) & 0xFF),
                static_cast<unsigned char>((a >> 8) & 0xFF),
                static_cast<unsigned char>(a & 0xFF) } } {}

    ipv4(ipv4 const & other) noexcept : data(other.data) {}
    ipv4 operator=(ipv4 const & other) noexcept {
        data = other.data;
        return *this;
    }

    string to_string() const {
        stringstream sstr;
        sstr << *this;
        return sstr.str();
    }

    constexpr unsigned long to_ulong() const noexcept {
        return (static_cast<unsigned long>(data[0]) << 24) |
               (static_cast<unsigned long>(data[1]) << 16) |
               (static_cast<unsigned long>(data[2]) << 8)  |
               static_cast<unsigned long>(data[3]);
    }

    friend ostream& operator<<(ostream& os, const ipv4& a) {
        os << static_cast<int>(a.data[0]) << '.'
           << static_cast<int>(a.data[1]) << '.'
           << static_cast<int>(a.data[2]) << '.'
           << static_cast<int>(a.data[3]);

        return os;
    }

    friend istream& operator>>(istream& is, ipv4& a) {
        char d1, d2, d3;
        int b1, b2, b3, b4;
        is >> b1 >> d1 >> b2 >> d2 >> b3 >> d3 >> b4;

        if (d1 == '.' && d2 == '.' && d3 == '.') {
            a = ipv4(b1, b2, b3, b4);
        }
        else {
            is.setstate(ios_base::failbit);
        }
        return is;
    }
};

and could be use as:

int main(int argc, char const *argv[])
{
    ipv4 address(192, 168, 1, 1);
    cout << address << endl;

    ipv4 ip;
    
    cout << ip << endl;
    cin >> ip;

    if (!cin.fail()) {
        cout << ip << endl;
    }

    return 0;
}

 My question is, how exactly could I avoid those alerts when parameter values are sent from the program (without using user input)?.

warning: unsigned conversion from 'int' to 'unsigned char' changes value from '9999' to '15' [-Woverflow] 69 | ipv4 address(9999, 9999, 9999, 9999);

input: 9999.9999.9999.9999
output: 15.15.15.15

Notes:

• Run this code returns null if an incorrect type or value is detected.
• This program requires a compiler and library support for the ISO C++ 2011.
• Example.