发送UDP，Socket operation on non-socket，初学

发送UDP，Socket operation on non-socket，初学，请指教
今天刚开始看TCP/IP详解：实现，第一个程序示例就出现了错误，望大家帮助！谢谢！

C/C++ code

#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#define BUFFSIZE 150int main(void){    struct sockaddr_in serv;    char buff[BUFFSIZE];    int sockfd, n;    if((sockfd = socket(PF_INET, SOCK_DGRAM, 0) < 0))        perror("socket error");    bzero((char*)&serv, sizeof(serv));    memset(buff, 0, BUFFSIZE);    serv.sin_family = AF_INET;    serv.sin_addr.s_addr = inet_addr("140.252.1.32");    serv.sin_port = htons(13);    if(n = sendto(sockfd, buff, BUFFSIZE, 0,                (struct sockaddr *)&serv, sizeof(serv)) != BUFFSIZE)        perror("sendto error");    if((n = recvfrom(sockfd, buff, BUFFSIZE, 0,                        (struct sockaddr *)NULL, (int*)NULL)) != BUFFSIZE)        perror("recvfrom error");    printf("%s\n", buff);    exit(0);}

运行后出现：
sendto error: Socket operation on non-socket
recvfrom error: Socket operation on non-socket

[解决办法]
楼主这样修改试试：

if((sockfd = socket(PF_INET, SOCK_DGRAM, 0) < 0))
perror("socket error");

改为：
if(((sockfd = socket(PF_INET, SOCK_DGRAM, 0)) < 0))
perror("socket error");

=优先级小于<
因此sockfd实际上=0，因此出现 Socket operation on non-socket错误
消息根本就没发送
[解决办法]
if((sockfd = socket(PF_INET, SOCK_DGRAM, 0) < 0))

'<'号的优先级比'='号的高,因此你的sockfd的值不是0,就是1
改成
if((sockfd = socket(PF_INET, SOCK_DGRAM, 0)) < 0)

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