如何确保 TCP 套接字在创建时已连接

发布于 2024-11-25 13:15:34 字数 1430 浏览 6 评论 0原文

我有一个发送 TCP 数据包的客户端应用程序。目前，我的应用程序执行以下操作：创建套接字、绑定并发送数据包。

struct sockaddr_in localaddress;
localaddress.sin_port = htons(0);
localaddress.sin_addr.s_addr = INADDR_ANY;

int socket;
socket = socket(AF_INET, SOCK_STREAM, 0));
bind(socket, (struct sockaddr *)&sin,sizeof(struct sockaddr_in) );

在另一个线程中，应用程序连接并发送数据包：

struct socketaddr_in remoteaddress;
// omitted: code to set the remote address/ port etc...
nRet = connect (socket, (struct sockaddr * ) & remoteaddress, sizeof (sockaddr_in ));
if (nRet == -1)
    nRet = WSAGetLastError();
if (nRet == WSAEWOULDBLOCK) {
    int errorCode = 0;
    socklen_t codeLen = sizeof(int);
    int retVal = getsockopt(
            socket, SOL_SOCKET, SO_ERROR, ( char * ) &errorCode, &codeLen );
    if (errorCode == 0 && retVal != 0)
        errorCode = errno;
}
/* if the connect succeeds, program calls a callback function to notify the socket is connected, which then calls send() */

现在我想为本地端口指定一个端口范围，因此我将代码更改为

nPortNumber = nPortLow;
localaddress.sin_port = htons(nPortNumber);

并在我的端口范围中循环 nPortNumber，例如（ 4000 - 5000 ），直到绑定成功。

由于我总是从低端口启动 nPortNumber，因此如果先前在同一端口上创建了套接字，我会收到 WSAEADDRINUSE 错误作为 errorCode，这对我来说太晚了，因为它已经通过了套接字创建阶段。（为什么我没有在bind（）或connect（）处获得WSAEADDRINUSE？）

有没有办法可以更早地获得WSAEADDRINUSE，或者有没有办法在绑定和连接的端口范围中创建套接字？

提前致谢！

原文

I have a client application that sends TCP packets. Currently, my application does this:
creates a socket, binds and sends the packets.

struct sockaddr_in localaddress;
localaddress.sin_port = htons(0);
localaddress.sin_addr.s_addr = INADDR_ANY;

int socket;
socket = socket(AF_INET, SOCK_STREAM, 0));
bind(socket, (struct sockaddr *)&sin,sizeof(struct sockaddr_in) );

And in another thread, the application connects and sends the packets:

struct socketaddr_in remoteaddress;
// omitted: code to set the remote address/ port etc...
nRet = connect (socket, (struct sockaddr * ) & remoteaddress, sizeof (sockaddr_in ));
if (nRet == -1)
    nRet = WSAGetLastError();
if (nRet == WSAEWOULDBLOCK) {
    int errorCode = 0;
    socklen_t codeLen = sizeof(int);
    int retVal = getsockopt(
            socket, SOL_SOCKET, SO_ERROR, ( char * ) &errorCode, &codeLen );
    if (errorCode == 0 && retVal != 0)
        errorCode = errno;
}
/* if the connect succeeds, program calls a callback function to notify the socket is connected, which then calls send() */

Now I want to specify a port range for local port, so I changed the code to

nPortNumber = nPortLow;
localaddress.sin_port = htons(nPortNumber);

and loops nPortNumber in my port range, e.g ( 4000 - 5000 ) until the bind succeeds.

Since I always start my nPortNumber from the low port, if a socket is previously created on the same port, I get the WSAEADDRINUSE error as errorCode, which is too late for me because it has already passed the socket creation stage. (Why didn't I get WSAEADDRINUSE at bind() or connect()?)

Is there a way I can get the WSAEADDRINUSE earlier or is there a way to create a socket in the port range that binds and connects?

Thanks in advance!

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