recv MSG_PEEK

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因为不清楚 MSG_PEEK 是否阻塞所以写代码测试。
结论:recv falg 为 MSG_PEEK 时候是阻塞的。

#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 1static 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;}

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