我目前在服务器和客户端之间传递消息时遇到问题 . 据我所知,我正在按照Beej's Socket Programming Tutorial概述的套接字编程的最佳实践 .
当我运行这两个进程时,recv()系统调用返回-1(错误),而不是接收的字节数 . 此外,当尝试输出buf时,有一堆gobbledygook字符 . 这是有道理的,因为错误 .
我想知道是否有人可以引导我朝着正确的方向指导我为什么遇到recv()的问题?以下是相关的代码片段 .
服务器:
struct sockaddr_storage their_addr;
socklen_t addr_size;
int sockfd, newfd, byte_count, status;
char buf[512];
struct addrinfo hints, *res;
// first, load up address structs with getaddrinfo():
memset(&hints, 0, sizeof hints);
hints.ai_family = PF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
// get address info, print stuff if error
if((status = getaddrinfo("nunki.usc.edu", "21957", &hints, &res)) !=0){
fprintf(stderr, "getaddrinfo error: %s\n", gai_strerror(status));
exit(1);
}
// make a socket:
if((sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol)) == -1){
cout << "socket fail" << endl;
}
// bind the socket to the port
bind(sockfd, res->ai_addr, res->ai_addrlen);
// required output
cout << "Phase1: Login server has TCP port number " << "21957 "
<< "and IP address " << getIPfromHost("nunki.usc.edu") << endl;
// listen for incoming connections
listen(sockfd, 10);
cout << "after listen" << endl;
// halt until receipt
addr_size = sizeof(their_addr);
newfd = accept(sockfd, (struct sockaddr *)&their_addr, &addr_size);
cout << "after accept" << endl;
// Now that we're connected, we can receive some data
byte_count = recv(sockfd, buf, sizeof buf, 0);
printf("recv()'d %d bytes of data in buf\n", byte_count);
printf("Msg is %s\n", buf);
客户:
struct addrinfo hints, *res;
int sockfd;
// first, load up address structs with getaddrinfo():
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
getaddrinfo("nunki.usc.edu", "21957", &hints, &res);
// make a socket:
if((sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol)) == -1){
cout << "socket fail" << endl;
}
// attempt connection to port
if(connect(sockfd, res->ai_addr, res->ai_addrlen) == -1){
cout << "connect fail" << endl;
}
// send message to server
cout << "sockfd " << sockfd << endl;
int byte_count = send(sockfd, "Hello", 5, 0);
cout << byte_count << endl;
以下是Server的输出:
Phase1: Login server has TCP port number 21957 and IP address 68.181.201.3
after listen
after accept
recv()'d -1 bytes of data in buf
Msg is ÿhÿ?sÈ
Glæ
以下是Client的输出:
sockfd 4
5
4 回答
你在错误的套接字上调用
recv
. 您需要recv
newfd
:现在已经不在了,
我完全不同意 .
您没有检查
listen
,bind
,getaddrinfo
等的退货状态程序中没有
strerror
或perror
你想recv()使用从accept()返回的套接字
也许我不应该把它作为答案,而是作为评论 . 不过,恕我直言,你使用
getaddrinfo()
对我来说似乎不对 .所以
通过这种方式,您可以检查所有可能的连接 .
getaddrinfo()
是相当不寻常的 . 通常,您将创建一个IPv6套接字并使其能够通过使用setsockopt()
取消设置IPV6_V6ONLY
标志来监听IPv4 . 通过这种方式,套接字可以同时监听IPv6和IPv4 . (唉,不是在WIndows XP AFAIK上 . )sockfd
仅用于监听客户端,newfd
用于数据传输 .