select收数据

之前写的服务器端 表示都无法收到client发的数据，找不到原因，原来是有个socket接收数据缓冲木有设置，现在设置后就可以正常收到数据啦！

server端：

#include <winsock.h>
#include <stdio.h>

#include <string>

#pragma comment(lib, "ws2_32.lib")

#define MYPORT 1234    // the port users will be connecting to
#define BACKLOG 5     // how many pending connections queue will hold
#define BUF_SIZE 200
int fd_A[BACKLOG];    // accepted connection fd
int conn_amount;    // current connection amount

void showclient()
{
    int i;
    printf("client amount: %d\n", conn_amount);
    for (i = 0; i < BACKLOG; i++) 
    {
    printf("[%d]:%d  ", i, fd_A[i]);
    }
    printf("\n\n");
}

int main(void)
{
    WSADATA     wsaData;
    WSAStartup(0x0202, &wsaData);
    int sock_fd, new_fd;  // listen on sock_fd, new connection on new_fd

    struct sockaddr_in server_addr;    // server address information
    struct sockaddr_in client_addr; // connector's address information
    int sin_size;
    int yes = 1;
    char buf[BUF_SIZE];
    int ret;
    int i;

    if ((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {

        perror("socket");
        exit(1);
    }

    //这一步很重要，不然数据可能收不到
    int nRecvBuf = 32 * 1024; //设置为32K
    if (setsockopt(sock_fd,SOL_SOCKET,SO_RCVBUF,(const char*)&nRecvBuf,sizeof(int)) == -1) {
        perror("setsockopt");
        exit(1);
    }

    server_addr.sin_family = AF_INET;         // host byte order
    server_addr.sin_port = htons(MYPORT);     // short, network byte order
    server_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP
    memset(server_addr.sin_zero, '\0', sizeof(server_addr.sin_zero));

    if (bind(sock_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) 
    {
        perror("bind");
        exit(1);
    }

    if (listen(sock_fd, BACKLOG) == -1) 
    {
        perror("listen");
        exit(1);
    }

    printf("listen port %d\n", MYPORT);

    fd_set fdsr;
    int maxsock;
    struct timeval tv;
    conn_amount = 0;
    sin_size = sizeof(client_addr);
    maxsock = sock_fd;

    while (1) 
    {
        FD_ZERO(&fdsr);

        FD_SET(sock_fd, &fdsr);
        // timeout setting
        tv.tv_sec = 10;
        tv.tv_usec = 0;
        // add active connection to fd set
        for (i = 0; i < BACKLOG; i++) 
        {
            if (fd_A[i] != 0)
            {
                FD_SET(fd_A[i], &fdsr);
            }
        }

        ret = select(maxsock + 1, &fdsr, NULL, NULL, &tv);
        if (ret < 0)
        {
            perror("select");
            break;

        } 
        else if (ret == 0) 
        {
            printf("timeout\n");
            continue;
        }

        // check every fd in the set
        for (i = 0; i < conn_amount; i++) 
        {
            if(fd_A[i] > 0)
            {
                if (FD_ISSET(fd_A[i], &fdsr)) 
                {
                    ret = recv(fd_A[i], buf, sizeof(buf), 0);
                    if (ret <= 0) 
                    {        // client close
                        printf("client[%d] close\n", i);
                        --conn_amount;
                        closesocket(fd_A[i]);
                        FD_CLR(fd_A[i], &fdsr);
                        fd_A[i] = 0;
                    } 
                    else 
                    {
                        if (ret < BUF_SIZE)
                            memset(&buf[ret], '\0', 1);
                        printf("client[%d] send:%s\n", i, buf);
                    }
                }
            }
        }
        // check whether a new connection comes
        if (FD_ISSET(sock_fd, &fdsr)) 
        {
            new_fd = accept(sock_fd, (struct sockaddr *)&client_addr, &sin_size);
            if (new_fd <= 0) 
            {
                perror("accept");
                continue;
            }
            // add to fd queue
            if (conn_amount < BACKLOG) 
            {
                for (int j = 0; j < BACKLOG; ++j)
                {
                    if (fd_A[j] == 0)
                    {
                        fd_A[j] = new_fd;
                        printf("new connection client[%d] %s:%d\n", conn_amount,inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
                        if (new_fd > maxsock)
                        {
                            maxsock = new_fd;
                        }
                        ++conn_amount;
                        break;
                    }
                }
            }
            else 
            {
                printf("max connections arrive, exit\n");
                send(new_fd, "bye", 4, 0);
                closesocket(new_fd);
                break;
            }
        }
    }
    // close other connections
    for (i = 0; i < BACKLOG; i++) 
    {
        if (fd_A[i] != 0) 
        {
            closesocket(fd_A[i]);
        }
    }
    exit(0);

}

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