recv MSG_PEEK

因爲不清楚 MSG_PEEK 是否阻塞所以寫代碼測試。
結論:recv falg 爲 MSG_PEEK 時候是阻塞的。

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <netdb.h>
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>

#define ANET_OK 0
#define ANET_ERR -1
#define ANET_ERR_LEN 256
#define ANET_CONNECT_NONE 0
#define ANET_CONNECT_NONBLOCK 1

static void anetSetError(char *err, const char *fmt, ...)
{
    va_list ap;

    if (!err) return;
    va_start(ap, fmt);
    vsnprintf(err, ANET_ERR_LEN, fmt, ap);
    va_end(ap);
}

static int anetTcpGenericConnect(char *err, char *addr, int port, int flags)
{
    int s, on = 1;
    struct sockaddr_in sa;

    if ((s = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        anetSetError(err, "creating socket: %s\n", strerror(errno));
        return -1;
    }
    /* Make sure connection-intensive things like the redis benckmark
     *      * will be able to close/open sockets a zillion of times */
    setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));

    sa.sin_family = AF_INET;
    sa.sin_port = htons(port);
    if (inet_aton(addr, &sa.sin_addr) == 0) {
        struct hostent *he;

        he = gethostbyname(addr);
        if (he == NULL) {
            anetSetError(err, "can't resolve: %s\n", addr);
            close(s);
            return -1;
        }
        memcpy(&sa.sin_addr, he->h_addr, sizeof(struct in_addr));
    }
    if (connect(s, (struct sockaddr*)&sa, sizeof(sa)) == -1) {
        if (errno == EINPROGRESS &&
                (flags & ANET_CONNECT_NONBLOCK) )
            return s;

        close(s);
        return -1;
    }
    return s;
}


int main()
{
    char err[1000] = { 0 };
    int fd = anetTcpGenericConnect( err, "127.0.0.1", 8080, ANET_CONNECT_NONBLOCK );
    if( fd < 0 )
    {
        printf( "err=%s\n", err );
        return -1;
    }
    char buf[100] = {0};

    int recvByte = recv( fd, buf, 100, MSG_PEEK );
    printf( "recvByte=%d,buf=%s\n", recvByte, buf );
    return 0;
}