Use find_if and function object to search for a vector of the custom type.

To implement NAT penetration, You need to search for the client's IP address and port at the same time. In this case, you need to customize the struct and then declare a vector of this type, each time a customer initiates a connection, he/she needs to search for this table. If the client's ip address and port exist, the system returns the result. Otherwise, the structure is added to the forwarding list.
# Include "stdafx. h"

# Include <iostream>

# Include <string>
# Include <functional>
# Include <list>
# Include <vector>
# Include <algorithm>
Using namespace std;

Typedef struct _ NAT
{
Char userip [30];
Int userport;
} NatType;
// Query class

Class FindIP
{
Public:
Bool operator () (natType & dValue)
{
Return (strcmp (dValue. userip, m_val.userip) = 0) & dValue. userport = m_val.userport;

}

Static void SetUserNat (natType dval)
{
M_val = dval;
}
Private:
Static natType m_val;
};

NatType natvalue, destvalue;
NatType FindIP: m_val = natvalue;
Int main (int argc, char * argv [])
{Vector <natType> userList;
NatType tempnat;
Strcpy (tempnat. userip, "192.168.0.1 ");
Tempnat. userport = 9000;
UserList. push_back (tempnat );
//, Destvalue;
Strcpy (natvalue. userip, "192.168.0.1 ");
Natvalue. userport = 9000;
FindIP: SetUserNat (natvalue );

Vector <natType>: iterator iter = find_if (userList. begin (), userList. end (), FindIP ());
If (iter = userList. end ())
{
/* Strcpy (destvalue. userip, (* iter). userip );
*/Destvalue. userport = (* iter). userport;
Printf ("nothing/n ");

UserList. push_back (natvalue );
}
 
Return 0;
}