连接数据库调用String类型的值失败

问题遇到的现象和发生背景

尝试调用String类型的值失败

用代码块功能插入代码，请勿粘贴截图
#include <iostream>
#include <pqxx/pqxx>
#include<string>
#include<string.h>
using namespace std;
using namespace pqxx;

int main(int argc, char* argv[]) {
    string na = "ecps_ecpsdb";
    string us = "ecps_ecpsdb_user";
    string pa = "wbbb";
    string ho = "10.19.133.75";
    string po = "4096";

    try {
        connection conn("dbname=na user=us password=pa \
    hostaddr=ho port=po");
        if (conn.is_open()) {
            cout << "connect to postgresql successfully. dbname=" << conn.dbname() << endl;
        }
        else {
            cout << "connect to postgresql fail." << endl;
            return 1;
        }
    }
        catch (const std::exception& e) {
            cerr << e.what() << endl;
            return 1;
        }
    
    return 0;
}
运行结果及报错内容

报错invalid integer value "po" for connection option "port"

我想要达到的结果

怎么调用string类型的值，使数据库能连接上

connection conn("dbname=na user=us password=pa hostaddr=ho port=po")
直接写进来connection conn("dbname=ecps_ecpsdb user=ecps_ecpsdb_user password=wbbb hostaddr=10.19.133.75 port=4096")