Winsock使用之创建客户端Socket_winsock sock

创建客户端Socket

初始化以后，SOCKET对象必须由客户端实例化

1.声明一个addrinfo对象，它包含一个sockaddr结构，然后初始化这些值。此应用程序，互联网地址族未指明，所以或者返回IPv6地址或者IPv4地址。应用程序要求socket类型为SOCK_STREAM（提供面向连接的稳定数据传输，即TCP协议）。

struct addrinfo *result = NULL,
  *ptr = NULL,
  hints;
 
ZeroMemory( &hints, sizeof(hints) );
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;

2.调用getaddrinfo函数为在命令行上输出的服务器请求IP地址。在这个示例中，客户端将要连接的服务器上的TCP端口DEFAULT_PORT 宏定义为 27015。getaddrinfo函数返回一整型，检查错误。

#define DEFAULT_PORT "27015"
 
// Resolve the server address and port
iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);
if (iResult != 0) {
  printf("getaddrinfo failed: %d\n", iResult);
  WSACleanup();
  return 1;
}

3.创建一个SOCKET 对象称为ConnectSocket。

SOCKET ConnectSocket = INVALID_SOCKET;

// Attempt to connect to the first address returned by// the call to getaddrinfo
ptr=result;
 
// Create a SOCKET for connecting to server
ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype,
    ptr->ai_protocol);

5.检查错误，保证 SOCKET 是有效的。

if (ConnectSocket == INVALID_SOCKET) {
    printf("Error at socket(): %ld\n", WSAGetLastError());
    freeaddrinfo(result);
    WSACleanup();
    return 1;
}

连接socket

// Connect to server.
iResult = connect( ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
if (iResult == SOCKET_ERROR) {
  closesocket(ConnectSocket);
  ConnectSocket = INVALID_SOCKET;
}
 
// Should really try the next address returned by getaddrinfo// if the connect call failed// But for this simple example we just free the resources// returned by getaddrinfo and print an error message
 
freeaddrinfo(result);
 
if (ConnectSocket == INVALID_SOCKET) {
  printf("Unable to connect to server!\n");
  WSACleanup();
  return 1;
}

• 客户端将要连接的服务器IP地址
• 客户端将要连接的服务器端口号，当客户端调用getaddrinfo 函数时，端口指定为 27015。

客户端发送和接收数据

#define DEFAULT_BUFLEN 512
 
int recvbuflen = DEFAULT_BUFLEN;
 
char *sendbuf = "this is a test";
char recvbuf[DEFAULT_BUFLEN];
 
int iResult;
 
// 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 for sending since no more data will be sent// the client can still use the ConnectSocket for receiving data
iResult = shutdown(ConnectSocket, SD_SEND);
if (iResult == SOCKET_ERROR) {
  printf("shutdown failed: %d\n", WSAGetLastError());
  closesocket(ConnectSocket);
  WSACleanup();
  return 1;
}
 
// Receive data until the server closes the connectiondo {
  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);

断开客户端

// shutdown the send half of 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;
}

2.当客户端应用程序完成接收数据时，closesocket函数被调用来关闭socket。当客户端应用程序完成后使用WS2_32.dll，WSACleanup 函数被调用以释放资源。

// cleanup
closesocket(ConnectSocket);
WSACleanup();
 
return 0;

编辑于2016年8月3日 By Seefun_Zhu