《Windows API巡礼》---send和recv

send函数用于在一个已经连接成功的socket上发送数据：

int send(

__in SOCKET s, //已连接的套接字

__in const char *buf,//指向将要发送数据的缓冲区

__in int len, //缓冲区数据的字节长度

__in int flags //指定数据传输方式：0---无特殊行为；MSG_DONTROUTE---传输层不要将它发出的包

//路由出去；MSG_OOB---数据应该被带外发送

);

其中，所谓带外数据，也可称为TCP紧急数据，它是在两个相连的每一对套接字间逻辑上独立的传输通道。带外数据是独立于普通数据传送给用户的。

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。

send函数实例如下：

#include <windows.h>

#include <winsock2.h>

#include <stdio.h>

#define DEFAULT_BUFLEN 512

#define DEFAULT_PORT 27015

int main() {

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

// Declare and initialize variables.

int iResult;

WSADATA wsaData;

SOCKET ConnectSocket;

struct sockaddr_in clientService;

int recvbuflen = DEFAULT_BUFLEN;

char *sendbuf = "Client: sending data test";

char recvbuf[DEFAULT_BUFLEN] = "";

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

// Initialize Winsock

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

if (iResult != NO_ERROR) {

printf("WSAStartup failed with error: %d/n", iResult);

return 1;

}

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

// Create a SOCKET for connecting to server

ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

if (ConnectSocket == INVALID_SOCKET) {

printf("socket failed with error: %ld/n", WSAGetLastError());

WSACleanup();

return 1;

}

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

// The sockaddr_in structure specifies the address family,

// IP address, and port of the server to be connected to.

clientService.sin_family = AF_INET;

clientService.sin_addr.s_addr = inet_addr( "127.0.0.1" );

clientService.sin_port = htons( DEFAULT_PORT );

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

// Connect to server.

iResult = connect( ConnectSocket, (SOCKADDR*) &clientService, sizeof(clientService) );

if (iResult == SOCKET_ERROR) {

printf( "connect failed with error: %d/n", WSAGetLastError() );

closesocket(ConnectSocket);

WSACleanup();

return 1;

}

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

// Send an initial buffer

iResult = send( ConnectSocket, sendbuf, (int)strlen(sendbuf), 0 );

if (iResult == SOCKET_ERROR) {

printf("send() failed with error: %d/n", WSAGetLastError());

closesocket(ConnectSocket);

WSACleanup();

return 1;

}

printf("Bytes Sent: %d/n", iResult);

// shutdown the connection since no more data will be sent

iResult = shutdown(ConnectSocket, SD_SEND);

if (iResult == SOCKET_ERROR) {

printf("shutdown failed with error: %d/n", WSAGetLastError());

closesocket(ConnectSocket);

WSACleanup();

return 1;

}

// Receive until the peer closes the connection

do {

iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);

if ( iResult > 0 )

printf("Bytes received: %d/n", iResult);

else if ( iResult == 0 )

printf("Connection closed/n");

else

printf("recv failed with error: %d/n", WSAGetLastError());

} while( iResult > 0 );

// cleanup

closesocket(ConnectSocket);

WSACleanup();

return 0;

}

revc函数用于从一个已经建立连接的socket出接收数据：

int recv(

__in SOCKET s, //准备接收数据的套接字

__out char *buf, //指向即将接收数据的字符缓冲区的指针

__in int len, //缓冲区的大小

__in int flags //指定传输控制方式：0---无特殊行为；MSG_PKKE---表示数据从接收端口复制到接收

//缓冲区中，并且没有从系统缓冲区中将数据删除；MSG_OOB---表示数据是带外发送的

);

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。

recv函数实例代码如下：

#include <windows.h>

#include <winsock2.h>

#include <stdio.h>

#define DEFAULT_BUFLEN 512

#define DEFAULT_PORT "27015"

int __cdecl main() {

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

// Declare and initialize variables.

WSADATA wsaData;

int iResult;

SOCKET ConnectSocket;

struct sockaddr_in clientService;

char *sendbuf = "this is a test";

char recvbuf[DEFAULT_BUFLEN];

int recvbuflen = DEFAULT_BUFLEN;

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

// Initialize Winsock

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

if (iResult != NO_ERROR) {

printf("WSAStartup failed: %d/n", iResult);

return 1;

}

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

// Create a SOCKET for connecting to server

ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

if (ConnectSocket == INVALID_SOCKET) {

printf("Error at socket(): %ld/n", WSAGetLastError() );

WSACleanup();

return 1;

}

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

// The sockaddr_in structure specifies the address family,

// IP address, and port of the server to be connected to.

clientService.sin_family = AF_INET;

clientService.sin_addr.s_addr = inet_addr( "127.0.0.1" );

clientService.sin_port = htons( 27015 );

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

// Connect to server.

iResult = connect( ConnectSocket, (SOCKADDR*) &clientService, sizeof(clientService) );

if ( iResult == SOCKET_ERROR) {

closesocket (ConnectSocket);

printf("Unable to connect to server: %ld/n", WSAGetLastError());

WSACleanup();

return 1;

}

// Send an initial buffer

iResult = send( ConnectSocket, sendbuf, (int)strlen(sendbuf), 0 );

if (iResult == SOCKET_ERROR) {

printf("send failed: %d/n", WSAGetLastError());

closesocket(ConnectSocket);

WSACleanup();

return 1;

}

printf("Bytes Sent: %ld/n", iResult);

// shutdown the connection since no more data will be sent

iResult = shutdown(ConnectSocket, SD_SEND);

if (iResult == SOCKET_ERROR) {

printf("shutdown failed: %d/n", WSAGetLastError());

closesocket(ConnectSocket);

WSACleanup();

return 1;

}

// Receive until the peer closes the connection

do {

iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);

if ( iResult > 0 )

printf("Bytes received: %d/n", iResult);

else if ( iResult == 0 )

printf("Connection closed/n");

else

printf("recv failed: %d/n", WSAGetLastError());

} while( iResult > 0 );

// cleanup

closesocket(ConnectSocket);

WSACleanup();

return 0;

}