从 UDP 套接字读取数据
我使用以下函数从文件描述符中读取...
int cread(int fd, char *buf, int n){
int nread;
if((nread=read(fd, buf, n))<0){
perror("Reading data");
exit(1);
}
return nread;
}
以下是使用上述函数的函数
if(FD_ISSET(tap_fd, &rd_set)){
/* data from tun/tap: just read it and write it to the network */
nread = cread(tap_fd, buffer, BUFSIZE);
tap2net++;
do_debug("TAP2NET %lu: Read %d bytes from the tap interface\n", tap2net, nread);
/* write length + packet */
plength = htons(nread);
nwrite = cwrite(net_fd, (char *)&plength, sizeof(plength));
nwrite = cwrite(net_fd, buffer, nread);
do_debug("TAP2NET %lu: Written %d bytes to the network\n", tap2net, nwrite);
}
它们都可以与 TCP siocket 一起正常工作，但不能与 udp 套接字一起工作..任何帮助将不胜感激
I use the following function to read from a file descriptor...
int cread(int fd, char *buf, int n){
int nread;
if((nread=read(fd, buf, n))<0){
perror("Reading data");
exit(1);
}
return nread;
}
Following is the function that uses the above function
if(FD_ISSET(tap_fd, &rd_set)){
/* data from tun/tap: just read it and write it to the network */
nread = cread(tap_fd, buffer, BUFSIZE);
tap2net++;
do_debug("TAP2NET %lu: Read %d bytes from the tap interface\n", tap2net, nread);
/* write length + packet */
plength = htons(nread);
nwrite = cwrite(net_fd, (char *)&plength, sizeof(plength));
nwrite = cwrite(net_fd, buffer, nread);
do_debug("TAP2NET %lu: Written %d bytes to the network\n", tap2net, nwrite);
}
They both work fine with TCP siocket but not with udp socket.. Any help would be appreciated
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目前尚不清楚您的问题到底是什么，但如果
net_fd是 UDP 套接字，则两个cwrite()调用将创建两个 UDP 数据报。在前面加上 UDP 的大小并没有多大意义 - UDP 会为您维护消息边界。因此，在 UDP 情况下，只需完全删除
plength部分即可。It's not clear exactly what your problem is, but if
net_fdis a UDP socket, then the twocwrite()calls will create two UDP datagrams.There isn't a great deal of point in prepending the size with UDP - UDP maintains the message boundaries for you. So in the UDP case, just remove the
plengthpart entirely.