《Windows API巡礼》---sendto和recvfrom

sendto函数用于将数据发送到指定的地址：

int sendto(

__in SOCKET s, //指定套接字（可能已连接）

__in const char *buf, //指向将要发送数据的缓冲区

__in int len, //缓冲区大小

__in int flags, //指定数据传输方式

__in const struct sockaddr *to, //可选的指针，指向存储目标套接字地址信息的sockaddr结构

__in int tolen //to参数指向结构的字节大小

);

返回值：

成功时，返回发送的字节数；

失败时，返回SOCKET_ERROR，调用WSAGetLastError函数查看进一步错误信息。

sendto函数实例如下：

#include <windows.h>

#include <stdio.h>

#include "winsock2.h"

// Link with Ws3_32.lib

void main() {

WSADATA wsaData;

SOCKET SendSocket;

sockaddr_in RecvAddr;

int Port = 27015;

char SendBuf[1024];

int BufLen = 1024;

//---------------------------------------------

// Initialize Winsock

WSAStartup(MAKEWORD(2,2), &wsaData);

//---------------------------------------------

// Create a socket for sending data

SendSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

//---------------------------------------------

// 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("192.168.1.1");

//---------------------------------------------

// Send a datagram to the receiver

printf("Sending a datagram to the receiver.../n");

sendto(SendSocket,

SendBuf,

BufLen,

0,

(SOCKADDR *) &RecvAddr,

sizeof(RecvAddr));

//---------------------------------------------

// When the application is finished sending, close the socket.

printf("Finished sending. Closing socket./n");

closesocket(SendSocket);

//---------------------------------------------

// Clean up and quit.

printf("Exiting./n");

WSACleanup();

return;

}

recvfrom函数用于接收数据报并存储发送方源地址信息：

int recvfrom(

__in SOCKET s, //指定一个绑定的socket

__out char *buf, //存放接到的数据的缓冲区

__in int len, //缓冲区字节大小

__in int flags, //指定传输控制方式

__out struct sockaddr *from, //可选的指针，函数成功返回后，

//指向存储源套接字地址信息的sockaddr结构

__inout_opt int *fromlen //from的字节大小

);

返回值：

成功时，返回接收的字节数；

失败时，返回SOCKET_ERROR，调用WSAGetLastError函数查看进一步错误信息。

recvfrom函数实例如下：

#include <windows.h>

#include <stdio.h>

#include "winsock2.h"

void main() {

WSADATA wsaData;

SOCKET RecvSocket;

sockaddr_in RecvAddr;

int Port = 27015;

char RecvBuf[1024];

int BufLen = 1024;

sockaddr_in SenderAddr;

int SenderAddrSize = sizeof(SenderAddr);

//-----------------------------------------------

// Initialize Winsock

WSAStartup(MAKEWORD(2,2), &wsaData);

//-----------------------------------------------

// Create a receiver socket to receive datagrams

RecvSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

//-----------------------------------------------

// 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);

bind(RecvSocket, (SOCKADDR *) &RecvAddr, sizeof(RecvAddr));

//-----------------------------------------------

// Call the recvfrom function to receive datagrams

// on the bound socket.

printf("Receiving datagrams.../n");

recvfrom(RecvSocket,

RecvBuf,

BufLen,

0,

(SOCKADDR *)&SenderAddr,

&SenderAddrSize);

//-----------------------------------------------

// Close the socket when finished receiving datagrams

printf("Finished receiving. Closing socket./n");

closesocket(RecvSocket);

//-----------------------------------------------

// Clean up and exit.

printf("Exiting./n");

WSACleanup();

return;

}