win7系统级socket缓冲区有多大？

seeyou_shj

进行网络程序极限测试时发现，通过调用socket发送/接收数据，有时候会有接收到的数据包里面的数据部分丢失的情况，应该是系统默认的socket缓冲区太小导致。网上搜了一下如何设置系统默认的缓冲区大小设置，找到一些资料，比如

• [HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet\Services\Afd\Parameters]
• DefaultReceiveWindow = 1800 (16进制)
• DefaultSendWindow = 1800（16进制）
• 可以设置Windows7修改socket默认缓冲区大小。
  

有个问题，不对其进行设置的情况下，默认的系统缓冲区有多大呢？是不是跟电脑内存有关？也就是说内存越大，系统默认的socket缓冲区越大？请大佬帮忙解惑，多谢！

禁闭岛

可以调用getsockopt函数设置SO_RCVBUF来获取

seeyou_shj

从MSDN官方网站找了个程序，测试了一下，结果返回0.
代码如下：

[C++] 纯文本查看 复制代码

#include <stdio.h>
#include <winsock2.h>
#include <windows.h>

int main() {

  //---------------------------------------
  // Declare variables
  WSADATA wsaData;
  SOCKET ListenSocket;
  sockaddr_in service;

  //---------------------------------------
  // Initialize Winsock
  int iResult = WSAStartup( MAKEWORD(2,2), &wsaData );
  if( iResult != NO_ERROR )
    printf("Error at WSAStartup\n");

  //---------------------------------------
  // Create a listening socket
  ListenSocket = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );
  if (ListenSocket == INVALID_SOCKET) {
    printf("Error at socket()\n");
    WSACleanup();
    return 0;
  }

  //---------------------------------------
  // Bind the socket to the local IP address
  // and port 27015
  hostent* thisHost;
  char* ip;
  u_short port;
  port = 27015;
  thisHost = gethostbyname("");
  ip = inet_ntoa (*(struct in_addr *)*thisHost->h_addr_list);

  service.sin_family = AF_INET;
  service.sin_addr.s_addr = inet_addr(ip);
  service.sin_port = htons(port);
 
  if ( bind( ListenSocket,(SOCKADDR*) &service, sizeof(service) )  == SOCKET_ERROR ) {
    printf("bind failed\n");
    closesocket(ListenSocket);
    return 0;
  }

  //---------------------------------------
  // Initialize variables and call getsockopt. 
  // The SO_ACCEPTCONN parameter is a socket option 
  // that tells the function to check whether the 
  // socket has been put in listening mode or not. 
  // The various socket options return different
  // information about the socket. This call should
  // return 0 to the optVal parameter, since the socket
  // is not in listening mode.
  int optVal;
  int optLen = sizeof(int);

  if (getsockopt(ListenSocket, 
    SOL_SOCKET, 
    SO_ACCEPTCONN, 
    (char*)&optVal, 
    &optLen) != SOCKET_ERROR)
    printf("SockOpt Value: %ld\n", optVal);

  //---------------------------------------
  // Put the listening socket in listening mode.
  if (listen( ListenSocket, 100 ) == SOCKET_ERROR) {
    printf("error listening\n");
  } 

  //---------------------------------------
  // Call getsockopt again to verify that 
  // the socket is in listening mode.
  if (getsockopt(ListenSocket, 
    SOL_SOCKET, 
    SO_ACCEPTCONN, 
    (char*)&optVal, 
    &optLen) != SOCKET_ERROR)
    printf("SockOpt Value: %ld\n", optVal);

  WSACleanup();
  return 0;
}

禁闭岛

SO_ACCEPTCONN这个选项是用来判断socket是否处于监听状态，程序的输出是正确的啊。

禁闭岛

[C] 纯文本查看 复制代码

#include <stdio.h>
#include <sys/socket.h>
#include <unistd.h>

int main(void)
{
	int bufsize = 0;
	int nLen = 0;

	int tcpfd = socket(AF_INET, SOCK_STREAM, 0);
	nLen = sizeof(bufsize);
	getsockopt(tcpfd, SOL_SOCKET, SO_RCVBUF, &bufsize, &nLen);
	printf("TCP RecvBuf = %d\n", bufsize);
	nLen = sizeof(bufsize);
	getsockopt(tcpfd, SOL_SOCKET, SO_SNDBUF, &bufsize, &nLen);
	printf("TCP SendBuf = %d\n", bufsize);

	int udpfd = socket(AF_INET, SOCK_DGRAM, 0);
	nLen = sizeof(bufsize);
	getsockopt(udpfd, SOL_SOCKET, SO_RCVBUF, &bufsize, &nLen);
	printf("UDP RecvBuf = %d\n", bufsize);
	nLen = sizeof(bufsize);
	getsockopt(udpfd, SOL_SOCKET, SO_SNDBUF, &bufsize, &nLen);
	printf("UDP SendBuf = %d\n", bufsize);

	close(tcpfd);
	close(udpfd);
	return 0;
}

这是linux系统查看socket发送/接收缓冲区大小的代码，windows也差不多。