我是UNIX新手,也是C语言编程新手。
我想做的是telnet
的简单实现。
我在两边做了所有需要的连接(Server &客户端).
在服务器上:我收到任何请求,我fork
一个新的进程来处理它
void createProcess() {
int pid = fork();
if( pid == CHILD ) {
transferHandling(s);
close(s);
_exit(0);
}
}
处理来自客户端的命令的方法:
int transferHandling(int socket) {
char buf[20];
char command[1024];
int n, pid, fd[2];
char *shell, *ps1;
if( checkLogin(socket) == 0 ) { // Used to check user account
send(socket, "Login Succeededn", 16, 0);
if( setupENV(info->name) == 0 ) { // setuid and setgid for the user
if( pipe(fd) == ERROR ) {
send(socket, "Server Busyn", 12, 0);
return 1;
}
// Here I make a process to run the default shell for the user
// and make pipe between them
if((pid = fork()) > 0) {
dup2(fd[0], STDOUT_FILENO);
close(fd[1]);
//read commands from socket
while(1) {
n = recv(socket, command, 1024, 0);
// send the commands received to the child which contains the default shell
write(fd[0], command, n);
}
} else {
dup2(fd[1], STDIN_FILENO);
dup2(socket, STDOUT_FILENO);
dup2(socket, STDERR_FILENO);
close(fd[0]);
//run default shell
shell = getpwnam(info->name)->pw_shell;
execlp(shell, shell, NULL);
}
} else {
return 1; // setup ENV error
}
} else {
send(socket, "Login Failedn", 13, 0);
}
}
这个程序可以成功运行与任何命令,但当客户端写入任何命令,如:wc, cd, bash (to run any other shell)
。程序被挂起。
连接建立后的客户端。
if(login(soc)) { // send the user information for the server
char cmd[2024], cc[1024];
int n;
while(1) {
printf("Readingn");
write(1, "username@hostname> ", 19);
n = read(0, cmd, 2024); // read the command from the STDIN, and send it to server
send(soc, cmd, n, 0);
printf("Receiving Nown");
n = recv(soc, cmd, 2024, 0); // getting back the command output
write(1, cmd, n);
}
}
您的管道文件描述符错误。你应该:
write(fd[1], ...);
:
dup2(fd[0], STDIN_FILENO);
顺便说一句,中间进程不需要从套接字读取命令并通过管道将它们发送到shell。您可以直接从套接字重定向shell的输入。此外,如果直接写入管道,则不需要dup2()
。最后,这样做的无限循环似乎是一个非常糟糕的主意,因为它会在shell死亡时旋转。