sending integers in winsock UDP

Fantasy (48)
Hello everyone
I'm trying to learn Winsock but I'm having few problems.
What i want is to send an integer that contain a number from the server to the client using UDP connection but i cant seem to figure out how.
I already know how to send char but don't know how to send an integer.

here is the source code:

Sender:- 
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#ifndef UNICODE
#define UNICODE
#endif

#define WIN32_LEAN_AND_MEAN

#include <winsock2.h>
#include <Ws2tcpip.h>
#include <stdio.h>
#include <iostream>

// Link with ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")

typedef struct t_MyStruct{
  int MyInt;
  int MyOtherInt;
}MyStruct;





int main()
{
	MyStruct ms;

	ms.MyInt=12345;
	ms.MyOtherInt=6789;

    int iResult;
    WSADATA wsaData;

    SOCKET SendSocket = INVALID_SOCKET;
    sockaddr_in RecvAddr;

    unsigned short Port = 27015;

	char SendBuf[2] = "H";
    int BufLen = 2;

    //----------------------
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != NO_ERROR) {
        wprintf(L"WSAStartup failed with error: %d\n", iResult);
        return 1;
    }

    //---------------------------------------------
    // Create a socket for sending data
    SendSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (SendSocket == INVALID_SOCKET) {
        wprintf(L"socket failed with error: %ld\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }
    //---------------------------------------------
    // Set up the RecvAddr structure with the IP address of
    // the receiver (in this example case "192.168.1.1")
    // and the specified port number.
    RecvAddr.sin_family = AF_INET;
    RecvAddr.sin_port = htons(Port);
    RecvAddr.sin_addr.s_addr = inet_addr("127.0.0.1");

    //---------------------------------------------
    // Send a datagram to the receiver
    wprintf(L"Sending a datagram to the receiver...\n");
    iResult = sendto(SendSocket,
                     SendBuf, 
					 BufLen, 
					 0,
					 (SOCKADDR *) & RecvAddr,
					 sizeof (RecvAddr));

    if (iResult == SOCKET_ERROR) {
        wprintf(L"sendto failed with error: %d\n", WSAGetLastError());
        closesocket(SendSocket);
        WSACleanup();
        return 1;
    }
    //---------------------------------------------
    // When the application is finished sending, close the socket.
    wprintf(L"Finished sending. Closing socket.\n");
    iResult = closesocket(SendSocket);
    if (iResult == SOCKET_ERROR) {
        wprintf(L"closesocket failed with error: %d\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }
    //---------------------------------------------
    // Clean up and quit.
    wprintf(L"Exiting.\n");
    WSACleanup();
	system("PAUSE");
    return 0;
}


Receiver:-

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#ifndef UNICODE
#define UNICODE
#endif

#define WIN32_LEAN_AND_MEAN

#include <winsock2.h>
#include <Ws2tcpip.h>
#include <stdio.h>
#include <iostream>

// Link with ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")



typedef struct t_MyStruct{
  int MyInt;
  int MyOtherInt;
}MyStruct;
	
int main()
{

MyStruct ms;
    int iResult = 0;

    WSADATA wsaData;

    SOCKET RecvSocket;
    sockaddr_in RecvAddr;

    unsigned short Port = 27015;

    char RecvBuf[2];
    int BufLen = 2;

    sockaddr_in SenderAddr;
    int SenderAddrSize = sizeof (SenderAddr);

    //-----------------------------------------------
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != NO_ERROR) {
        wprintf(L"WSAStartup failed with error %d\n", iResult);
        return 1;
    }
    //-----------------------------------------------
    // Create a receiver socket to receive datagrams
    RecvSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (RecvSocket == INVALID_SOCKET) {
        wprintf(L"socket failed with error %d\n", WSAGetLastError());
        return 1;
    }
    //-----------------------------------------------
    // Bind the socket to any address and the specified port.
    RecvAddr.sin_family = AF_INET;
    RecvAddr.sin_port = htons(Port);
    RecvAddr.sin_addr.s_addr = htonl(INADDR_ANY);

    iResult = bind(RecvSocket, (SOCKADDR *) & RecvAddr, sizeof (RecvAddr));
    if (iResult != 0) {
        wprintf(L"bind failed with error %d\n", WSAGetLastError());
        return 1;
    }
    //-----------------------------------------------
    // Call the recvfrom function to receive datagrams
    // on the bound socket.
    wprintf(L"Receiving datagrams...\n");
    iResult = recvfrom(RecvSocket,
                       RecvBuf, BufLen, 0, (SOCKADDR *) & SenderAddr, &SenderAddrSize);
    if (iResult == SOCKET_ERROR) {
        wprintf(L"recvfrom failed with error %d\n", WSAGetLastError());
    }
 
    //-----------------------------------------------
    // Close the socket when finished receiving datagrams
    wprintf(L"Finished receiving. Closing socket.\n");
    iResult = closesocket(RecvSocket);
    if (iResult == SOCKET_ERROR) {
        wprintf(L"closesocket failed with error %d\n", WSAGetLastError());
        return 1;
    }

    //-----------------------------------------------
    // Clean up and exit.
	std::cout <<RecvBuf;
    wprintf(L"Exiting.\n");
    WSACleanup();
	system("PAUSE");
    return 0;
}
shacktar (1187)
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//client

int integerToSend = some_integer();
int integerWithCorrectByteOrder = htonl(integerToSend);

iResult = sendto(SendSocket, (char*) &integerWithCorrectByteOrder, sizeof(int), 0,
                 (SOCKADDR *) & RecvAddr, sizeof (RecvAddr));


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//server

int integerFromClient = 0;

iResult = recvfrom(RecvSocket, (char*) &integerFromClient, sizeof(int), 0,
                   (SOCKADDR *) & SenderAddr, &SenderAddrSize);

int integerWithCorrectByteOrder = ntohl(integerFromClient);

Fantasy (48)
there is a small problem, when i try to send number 18 i receive 301989888 !! 


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//Server


int Some_number()
{
	return 18;
};
......

int integerToSend = Some_number();
	
int integerWithCorrectByteOrder = htonl(integerToSend);

iResult = sendto(
			SendSocket,
			(char*) &integerWithCorrectByteOrder,
			sizeof(int),
			0,
			(SOCKADDR *) & RecvAddr,
			sizeof (RecvAddr)
			);

std::cout << integerToSend;
					


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//Client
int integerFromClient = NULL;

int integerWithCorrectByteOrder = ntohl(integerFromClient);
	
iResult = recvfrom(	
                                RecvSocket,
				(char*) &integerFromClient,
				sizeof(int),
				0,
				(SOCKADDR *) & SenderAddr,
				&SenderAddrSize
			);
std::cout << integerFromClient;
Last edited on
Computergeek01 (5613)
The second argument for the "sendto(...)" function needs a char pointer so:

- Cast the data you send to a char, send it, then on the recieving end cast it back to an integer when it arrives. This requires that you know that you are recieving an integer from the sender so I don't recommend it.

- Send the char character equivalent to the reciever and use something like "isdigit(...)" from the ctype header to determine if it is a numerical character. Then use Stringstream to convert it back to an integer.

Stuff like this is better off in the Windows section because it deals specifically with the Win32 API.
Last edited on
shacktar (1187)
Fixing your client code:

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//Client
int integerFromClient = 0;

int integerWithCorrectByteOrder = ntohl(integerFromClient);
	
iResult = recvfrom(	
                                RecvSocket,
				(char*) &integerFromClient,
				sizeof(int),
				0,
				(SOCKADDR *) & SenderAddr,
				&SenderAddrSize
			);

int integerWithCorrectByteOrderFromClient = ntohl(integerFromClient);

std::cout << integerWithCorrectByteOrderFromClient ;
Fantasy (48)
@Computergeek01
i'll try do what you said but just to be honest i don't know how to do any of what you said, but google is my friend xD

@shacktar
oo sorry about that, i fixed it but its still giving me the same thing.
Fantasy (48)
WOW i did it xD
the server sent 550 and the Client received 550 :D LOL.

Here is the working code:-

Server:- 
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#include <winsock2.h>
#include <iostream>

// Link with ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")

int main()
{
    int iResult;
    WSADATA wsaData;

    SOCKET SendSocket = INVALID_SOCKET;
    sockaddr_in RecvAddr;

    unsigned short Port = 27015;

    char SendBuf[1024] = "550" ;
    int BufLen = 1024;

    //----------------------
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != NO_ERROR) {
        wprintf(L"WSAStartup failed with error: %d\n", iResult);
        return 1;
    }

    //---------------------------------------------
    // Create a socket for sending data
    SendSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (SendSocket == INVALID_SOCKET) {
        wprintf(L"socket failed with error: %ld\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }
    //---------------------------------------------
    // Set up the RecvAddr structure with the IP address of
    // the receiver (in this example case "127.0.0.1")
    // and the specified port number.
    RecvAddr.sin_family = AF_INET;
    RecvAddr.sin_port = htons(Port);
    RecvAddr.sin_addr.s_addr = inet_addr("127.0.0.1");

    //---------------------------------------------
    // Send a datagram to the receiver
	wprintf(L"Sending 550 to the receiver...\n");
    iResult = sendto(SendSocket,
                     SendBuf, BufLen, 0, (SOCKADDR *) & RecvAddr, sizeof (RecvAddr));
    if (iResult == SOCKET_ERROR) {
        wprintf(L"sendto failed with error: %d\n", WSAGetLastError());
        closesocket(SendSocket);
        WSACleanup();
        return 1;
    }
    //---------------------------------------------
    // When the application is finished sending, close the socket.
    wprintf(L"Finished sending. Closing socket.\n");
    iResult = closesocket(SendSocket);
    if (iResult == SOCKET_ERROR) {
        wprintf(L"closesocket failed with error: %d\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }
    //---------------------------------------------
    // Clean up and quit.
    wprintf(L"Exiting.\n");
    WSACleanup();
	system("PAUSE");
    return 0;
}



Client: 
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#include <winsock2.h>
#include <iostream>

// Link with ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")

int main()
{

    int iResult = 0;

    WSADATA wsaData;

    SOCKET RecvSocket;
    sockaddr_in RecvAddr;

    unsigned short Port = 27015;

    char RecvBuf[1024];
    int BufLen = 1024;

    sockaddr_in SenderAddr;
    int SenderAddrSize = sizeof (SenderAddr);

    //-----------------------------------------------
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != NO_ERROR) {
        wprintf(L"WSAStartup failed with error %d\n", iResult);
        return 1;
    }
    //-----------------------------------------------
    // Create a receiver socket to receive datagrams
    RecvSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (RecvSocket == INVALID_SOCKET) {
        wprintf(L"socket failed with error %d\n", WSAGetLastError());
        return 1;
    }
    //-----------------------------------------------
    // Bind the socket to any address and the specified port.
    RecvAddr.sin_family = AF_INET;
    RecvAddr.sin_port = htons(Port);
    RecvAddr.sin_addr.s_addr = htonl(INADDR_ANY);

    iResult = bind(RecvSocket, (SOCKADDR *) & RecvAddr, sizeof (RecvAddr));
    if (iResult != 0) {
        wprintf(L"bind failed with error %d\n", WSAGetLastError());
        return 1;
    }
    //-----------------------------------------------
    // Call the recvfrom function to receive datagrams
    // on the bound socket.
    wprintf(L"Receiving datagrams...\n");
    iResult = recvfrom(RecvSocket,
                       RecvBuf, BufLen, 0, (SOCKADDR *) & SenderAddr, &SenderAddrSize);

	std::cout<< std::endl << "RecvBuf is: " << RecvBuf << std::endl << std::endl;
    
	int Number = atoi(RecvBuf) ;

	std::cout<< std::endl << "after converting char (RecvBuf) to int (Number): " << Number << std::endl << std::endl;
	
	std::cout<< std::endl << "after adding 4 to the variable Number: " << Number+4 << std::endl << std::endl;

	if (iResult == SOCKET_ERROR) {
        wprintf(L"recvfrom failed with error %d\n", WSAGetLastError());
    }
 
    //-----------------------------------------------
    // Close the socket when finished receiving datagrams
    wprintf(L"Finished receiving. Closing socket.\n");
    iResult = closesocket(RecvSocket);
    if (iResult == SOCKET_ERROR) {
        wprintf(L"closesocket failed with error %d\n", WSAGetLastError());
        return 1;
    }

    //-----------------------------------------------
    // Clean up and exit.
    wprintf(L"Exiting.\n");
    WSACleanup();
	system("PAUSE");
    return 0;
}
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