03.UDP sockets and raw sockets

UDP socket

Note that in UDP sockets, recvfrom and sendto are used

  • API:

    • recvfrom:

      Receive packets and store source address (UDP)

    • Function prototype:

      int WSAAPI recvfrom(
  [in] SOCKET s,
  [out] char *buf,
  [in] int len,
  [in] int flags,
  [out] sockaddr *from,
  [in, out, optional] int *fromlen
);

    • parameter:

      • s: descriptor identifying the bound socket
      • buf: buffer for incoming data
      • len: buffer length
      • flags: used to modify function calling behavior
      • from: Pointer to sockaddr structure, the source address will be retained in this buffer
      • fromlen: size of the buffer pointed to by from

    • return value:

      If no error occurred, the recvfrom function returns the number of bytes received

  • UDP Server:

    #define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <iostream>
#include <WinSock2.h>
#pragma comment(lib,"ws2_32.lib")

int main() {<!-- -->
WORD wVersionRequested = MAKEWORD(2, 2);
WSAData lpWSAData;
if (WSAStartup(wVersionRequested, & amp;lpWSAData)) {<!-- -->
std::cout << "WSAStartup Error!" << std::endl;
return -1;
}

//SOCKADDR_IN structure is used to specify the transmission address and port of the AF_INET address series
sockaddr_in saddr;
saddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
saddr.sin_family = AF_INET;
saddr.sin_port = htons(50123);

SOCKET sock = socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) {<!-- -->
return -1;
}
char opt;
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, & amp;opt, sizeof(opt));

int nRet = bind(sock, (sockaddr*) & amp;saddr, sizeof(saddr));

sockaddr_in raddr;
int nLength = sizeof(sockaddr);
char szReadBuffer[50]{<!-- --> 0 };
while (true) {<!-- -->
nRet = recvfrom(sock, szReadBuffer, 50, 0, (sockaddr*) & amp;raddr, & amp;nLength);
if (nRet < 0) {<!-- -->
return -1;
}
std::cout << "data:" << szReadBuffer << std::endl;
std::cout << "Please enter:";
char szBuffer[50]{<!-- --> 0 };
std::cin >> szBuffer;
sendto(sock, szBuffer, strlen(szBuffer), 0, (sockaddr*) & amp;raddr, sizeof(sockaddr));
}
WSACleanup();
system("pause");
return 0;
}

  • UDP Client：

    #define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <iostream>
#include <WinSock2.h>
#pragma comment(lib,"ws2_32.lib")

int main() {<!-- -->

WORD wVersionRequested = MAKEWORD(2, 2);
WSAData lpWSAData;
WSAStartup(wVersionRequested, & lpWSAData);

sockaddr_in saddr;
saddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
saddr.sin_family = AF_INET;
saddr.sin_port = htons(50123);

SOCKET SocClient = socket(AF_INET, SOCK_DGRAM, 0);
if (SocClient < 0) {<!-- -->
return -1;
}

char opt;
setsockopt(SocClient, SOL_SOCKET, SO_REUSEADDR, & amp;opt, sizeof(opt));

char szSendBuffer[50]{<!-- --> 0 };
char szReadBuffer[50]{<!-- --> 0 };
sockaddr_in raddr;
int nLength = sizeof(raddr);
while (true) {<!-- -->
std::cout << "Please enter:";
std::cin >> szSendBuffer;
sendto(SocClient, szSendBuffer, strlen(szSendBuffer), 0, (sockaddr*) & amp;saddr, sizeof(sockaddr));
recvfrom(SocClient, szReadBuffer, 50, 0, (sockaddr*) & amp;raddr, & amp;nLength);
std::cout << "Server:" << szReadBuffer << std::endl;
}
closesocket(SocClient);
WSACleanup();
system("pause");
return 0;
}

Raw socket

  • Server: 
    #define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <iostream>
#include <WinSock2.h>
#pragma comment(lib,"ws2_32.lib")

typedef struct _IP_HEADER {<!-- -->
//Version information, header length
char cVersionAndHeaderLen;
\t//Service type
char vTypeOfServer;
//Data packet length
short sTotalLenOfPacket;
//Packet ID
short sPacketID;
//fragmentation information
short sSliceinfp;
//survival time
char cTTL;
\t//agreement type
char cTypeOfProtocol;
//Header checksum
short sCheckSum;
//Source IP address
unsigned int uiSrcIP;
//Destination IP address
unsigned int uiDestIP;
}IP_HEADER, *pIP_HEADER;

typedef struct _UDP_HEADER {<!-- -->
//Source port number
unsigned short usSourPort;
//destination port number
unsigned short usDestIPPort;
//Data packet length
unsigned short usLength;
//checksum
unsigned short usCheckSum;
}UDP_HEADER, pUDP_HEADER;

int main() {<!-- -->
WORD wVersionRequested = MAKEWORD(2, 2);
WSAData lpWSAData;
WSAStartup(wVersionRequested, & lpWSAData);

sockaddr_in SAddr;
SAddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
SAddr.sin_family = AF_INET;
SAddr.sin_port = htons(50123);
\t
SOCKET SocSrv = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
if (SocSrv < 0) {<!-- -->
return -1;
}

char opt;
setsockopt(SocSrv, SOL_SOCKET, SO_REUSEADDR, & amp;opt, sizeof(opt));

int nRet = bind(SocSrv, (sockaddr*) & amp;SAddr, sizeof(SAddr));
if (nRet < 0) {<!-- -->
return -1;
}

char szReadBuffer[500]{<!-- --> 0 };
sockaddr_in raddr;
int nLength = sizeof(sockaddr);
while (true) {<!-- -->
std::cout << "waiting......" << std::endl;
nRet = recvfrom(SocSrv, szReadBuffer, 500, 0, (sockaddr*) & amp;raddr, & amp;nLength);
IP_HEADER iph;
UDP_HEADER udph;
memcpy( & amp;iph, szReadBuffer, 20);
memcpy( & amp;udph, szReadBuffer + 20, 8);
int srcp = ntohs(udph.usSourPort);
in_addr ias, iad;
ias.s_addr = iph.uiSrcIP;
iad.s_addr = iph.uiDestIP;
char Temp[0x100]{<!-- --> 0 };
strcpy_s(Temp, inet_ntoa(iad));
std::cout << "SrcIP:" << inet_ntoa(iad) << "Port:" << ntohs(udph.usSourPort) << std::endl;
std::cout << "DestIP:" << inet_ntoa(iad) << "Port:" << ntohs(udph.usDestIPPort) << std::endl;
std::cout << "recv data:" << szReadBuffer + 28 << std::endl;
}
closesocket(SocSrv);
WSACleanup();
system("pause");
return 0;
}
  • Client: 
    #define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <iostream>
#include <WinSock2.h>
#pragma comment(lib,"ws2_32.lib")

int main() {<!-- -->

WORD wVerSionRequested = MAKEWORD(2, 2);
WSAData lpWSAData;
WSAStartup(wVerSionRequested, & amp;lpWSAData);

sockaddr_in saddr;
saddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
saddr.sin_family = AF_INET;
saddr.sin_port = htons(50123);
\t
SOCKET SocClient = socket(AF_INET, SOCK_DGRAM, 0);
if (SocClient < 0) {<!-- -->
return -1;
}

char opt;
setsockopt(SocClient, SOL_SOCKET, SO_REUSEADDR, & amp;opt, sizeof(opt));

char szSendBuffer[500]{<!-- --> 0 };
std::cout << "input:";
std::cin >> szSendBuffer;
sendto(SocClient, szSendBuffer, strlen(szSendBuffer), 0, (sockaddr*) & amp;s5addr, sizeof(sockaddr)); WSACleanup();
closesocket(SocClient);
WSACleanup();
system("pause");
return 0;
}