我有以下代码。
此代码用于TFTP服务器,该服务器为每个接收的请求创建一个fork或一个线程。我的问题在于线程方法。
E.g我从服务器请求30个文件,应该创建30个线程并将所请求的文件提供给客户端,每个线程将发送每个文件。
如果我使用pthread_join
(已注释),则代码可以正常运行,但如果我没有pthread_join
,则它会正确提供一些文件,但其中一些文件已损坏或为空。
我认为这是一个同步问题所以我试图为每个客户端文件描述符malloc
一块内存,所以一个线程只能修改它自己的文件描述符但没有运气。以下代码适用于某些
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <dirent.h>
#include <pthread.h>
#define BUFSIZE 8096
#define OperationMode 1
#if OperationMode
typedef struct {
int * fd;
int hit;
} THREAD_ARGS;
void *attendFTP(void *);
#endif
int ftp(int fd, int hit);
void getFunction(int fd, char * fileName);
void putFunction(int fd, char * fileName);
char * listFilesDir(char * dirName);
void lsFunction(int fd, char * dirName);
void mgetFunction(int fd, char *dirName);
/* just checks command line arguments, setup a listening socket and block on accept waiting for clients */
int main(int argc, char **argv) {
int i, port, pid, listenfd, socketfd, hit;
socklen_t length;
static struct sockaddr_in cli_addr; /* static = initialised to zeros */
static struct sockaddr_in serv_addr; /* static = initialised to zeros */
if (argc < 3 || argc > 3 || !strcmp(argv[1], "-?")) {
printf("\n\nhint: ./tftps Port-Number Top-Directory\n\n""\ttftps is a small and very safe mini ftp server\n""\tExample: ./tftps 8181 ./fileDir \n\n");
exit(0);
}
if (chdir(argv[2]) == -1) {
printf("ERROR: Can't Change to directory %s\n", argv[2]);
exit(4);
}
printf("LOG tftps starting %s - pid %d\n", argv[1], getpid());
/* setup the network socket */
if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
printf("ERROR system call - setup the socket\n");
port = atoi(argv[1]);
if (port < 0 || port > 60000)
printf("ERROR Invalid port number (try 1->60000)\n");
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(port);
if (bind(listenfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
printf("ERROR system call - bind error\n");
if (listen(listenfd, 64) < 0)
printf("ERROR system call - listen error\n");
// Main LOOP
for (hit = 1 ;; hit++) {
length = sizeof(cli_addr);
/* block waiting for clients */
socketfd = accept(listenfd, (struct sockaddr *) &cli_addr, &length);
if (socketfd < 0)
printf("ERROR system call - accept error\n");
else
{
#if OperationMode
pthread_t thread_id;
THREAD_ARGS *args = malloc(sizeof(THREAD_ARGS));
int * sockAUX = (int *) malloc(sizeof(int *));
*sockAUX = socketfd;
args->fd = sockAUX;
args->hit = hit;
if (args != NULL) {
if (pthread_create(&thread_id, NULL, &attendFTP, args)) {
perror("could not create thread");
return 1;
}
}
//pthread_join(thread_id,NULL);
#else
pid = fork();
if(pid==0) {
ftp(socketfd, hit);
} else {
//Temos de fechar o socketfd para que seja apenas a child a tratar dos pedidos, caso contrário iria ficar aqui pendurado
close(socketfd);
kill(pid, SIGCHLD);
}
#endif
}
}
}
#if OperationMode
void *attendFTP(void *argp) {
THREAD_ARGS *args = argp;
int sock = *args->fd;
printf("FD SOCK: %d\n\n", sock);
ftp(sock, args->hit);
free(args);
//printf("Thread executou\n\n");
pthread_exit(NULL);
return NULL;
}
#endif
/* this is the ftp server function */
int ftp(int fd, int hit) {
int j, file_fd, filedesc;
long i, ret, len;
char * fstr;
static char buffer[BUFSIZE + 1]; /* static so zero filled */
printf("FD: %d\n\n", fd);
ret = read(fd, buffer, BUFSIZE); // read FTP request
if (ret == 0 || ret == -1) { /* read failure stop now */
close(fd);
return 1;
}
if (ret > 0 && ret < BUFSIZE) /* return code is valid chars */
buffer[ret] = 0; /* terminate the buffer */
else
buffer[0] = 0;
for (i = 0; i < ret; i++) /* remove CF and LF characters */
if (buffer[i] == '\r' || buffer[i] == '\n')
buffer[i] = '*';
printf("LOG request %s - hit %d\n", buffer, hit);
/* null terminate after the second space to ignore extra stuff */
for (i = 4; i < BUFSIZE; i++) {
if (buffer[i] == ' ') { /* string is "GET URL " +lots of other stuff */
buffer[i] = 0;
break;
}
}
if (!strncmp(buffer, "get ", 4)) {
// GET
getFunction(fd, &buffer[5]);
} else if (!strncmp(buffer, "ls ", 3)) {
// LS
lsFunction(fd,&buffer[3]);
} else if (!strncmp(buffer, "mget ", 4)) {
// MGET
mgetFunction(fd, &buffer[5]);
}
sleep(1); /* allow socket to drain before signalling the socket is closed */
close(fd);
return 0;
}
void getFunction(int fd, char * fileName){
int file_fd;
long ret;
printf("FD GET: %d\n\n", fd);
static char buffer[BUFSIZE + 1]; /* static so zero filled */
if ((file_fd = open(fileName, O_RDONLY)) == -1) { /* open the file for reading */
printf("ERROR failed to open file %s\n", fileName);
printf("Err: %d\n\n",errno);
sprintf(buffer, "%s", "erro");
write(fd,buffer,BUFSIZE);
close(fd);
return;
}
printf("GET -> LOG SEND %s \n", fileName);
/* send file in 8KB block - last block may be smaller */
while ((ret = read(file_fd, buffer, BUFSIZE)) > 0) {
write(fd, buffer, ret);
}
}
void lsFunction(int fd, char * dirName){
printf("LS -> LOG Header %s \n", dirName);
static char buffer[BUFSIZE + 1];
sprintf(buffer, "%s", listFilesDir(dirName));
write(fd,buffer,BUFSIZE);
}
void mgetFunction(int fd, char *dirName)
{
FILE *fp;
char path[255];
static char buffer[BUFSIZE + 1];
printf("MGET COUNT -> LOG Header %s \n", dirName);
sprintf(buffer, "%s", listFilesDir(dirName));
write(fd,buffer,BUFSIZE);
}
char * listFilesDir(char * dirName)
{
DIR *midir;
struct dirent* info_archivo;
struct stat fileStat;
char fullpath[256];
char *files = malloc (sizeof (char) * BUFSIZE);
if ((midir=opendir(dirName)) == NULL)
{
return "\nO directorio pedido não existe.\n";
}
while ((info_archivo = readdir(midir)) != 0)
{
strcpy (fullpath, dirName);
strcat (fullpath, "/");
strcat (fullpath, info_archivo->d_name);
if (!stat(fullpath, &fileStat))
{
if(!S_ISDIR(fileStat.st_mode))
{
strcat (files, info_archivo->d_name);
strcat (files, "$$");
}
} else {
return "\nErro ao ler o directório.\n";
}
}
closedir(midir);
return files;
}
这是服务器的日志示例
LOG tftps从8181开始 - pid 15416 FD SOCK:4
FD:4LOG请求ls。 - 命中1 LS - &gt;日志标题。 FD SOCK:5
FD:5LOG请求mget。 - 命中2 MGET COUNT - &gt;日志标题。 FD SOCK:4
FD:4FD SOCK:5
FD:5LOG请求获取/.gitconfig - 命中4 FD GET:5
GET - &gt; LOG SEND .gitconfig LOG请求获取/
错误无法打开文件
FD SOCK:4
FD:4LOG请求获取/ghostdriver.log - 命中6 FD GET:4
GET - &gt; LOG SEND ghostdriver.log FD SOCK:8
FD:8
LOG请求获取/.bash_history - 命中7 FD GET:8
GET - &gt; LOG SEND .bash_history FD SOCK:6
FD:6LOG请求获取/.profile - 命中5 FD GET:6
GET - &gt; LOG SEND .profile FD SOCK:10
FD:10LOG请求获取/.ICEauthority - 命中8 FD GET:10
GET - &gt; LOG SEND .ICEauthority FD SOCK:13
FD:13 FD SOCK:14 FD SOCK:22 FD:22FD SOCK:16
FD SOCK:27 FD:27 FD SOCK:18 FD:18 FD SOCK:19LOG请求获取/.gtk-bookmarks - 命中14 FD SOCK:25
FD:25FD SOCK:15
LOG请求获取/.bashrc - 命中20 LOG请求获取/.bashrc - 命中9 FD GET:18
FD GET:25
FD GET:13
GET - &gt; LOG SEND .bashrc GET - &gt; LOG SEND .bashrc FD SOCK:23
FD:23LOG请求获取/.zshrc - 命中18 FD SOCK:26
FD:26FD GET:23
FD SOCK:29 FD:29GET - &gt; LOG SEND .bash_logoutks GET - &gt; LOG SEND .bash_logout FD SOCK: 17
FD:17LOG请求获取/.zsh-update - 命中13 LOG请求获取/.zsh-update - 命中22 FD SOCK:28
FD GET:27
FD:14LOG请求获取/.nano_history - 点击10 LOG请求获取/.nano_history - 点击24 LOG请求获取/.nano_history - 点击21 FD:16
LOG请求获取/.zsh_history - 命中12 FD SOCK:21
FD:21FD GET:16
FD:19LOG请求获取/.selected_editor - 命中15 FD SOCK:24
FD:24 FD:15FD GET:14
FD GET:17
FD GET:29
GET - &gt; LOG SEND .zcompdump-MacPearl-5.0.2 LOG请求获取 /.zcompdump-MacPearl-5.0.2 - 命中17 FD:28
LOG请求获取/.Xauthority - 命中23 GET - &gt; LOG SEND .Xauthority GET - &GT; LOG SEND .Xauthority FD GET:28
LOG请求获取/.Xauthority - 命中11 GET - &gt; LOG SEND .Xauthority FD GET:15
GET - &gt; LOG SEND .Xauthority GET - &gt; LOG SEND .Xauthority FD GET:19
FD GET:26
GET - &gt; LOG SEND .Xauthority LOG请求获取/.Xauthority - 命中16 FD GET:21
GET - &gt; LOG SEND .Xauthority FD GET:22
LOG请求获取/.Xauthority - 命中19 GET - &gt; LOG SEND .Xauthority GET - &GT; LOG SEND .Xauthority GET - &gt; LOG SEND .Xauthority FD GET:24
GET - &gt; LOG SEND .Xauthority FD SOCK:30
FD:30FD SOCK:31
FD:31LOG请求获取/.zcompdumpy - 点击25 LOG请求获取/.zcompdump - 命中26 FD GET:30
FD GET:31
GET - &gt; LOG SEND .zcompdump GET - &gt; LOG SEND .zcompdump
我可以看到有时他在多个线程中使用相同的文件描述符。我无法弄清楚如何解决这个同步问题。
答案 0 :(得分:1)
在声明中删除'static'存储限定符,例如:
静态字符缓冲区[BUFSIZE + 1];
您不能在可以从多个线程访问的数据上自由使用静态限定符 - 全局只有一个此类数据的实例,除非应用额外的显式同步,否则线程会将数据切碎并切片
如果使用自动存储,则所有常见的C编译器都会将数据放在当前堆栈中。有多个线程,即。多个堆栈,这意味着每个线程有一个数据项,因此没有切片和切块。
请注意,代码中的静态缓冲区有一个注释:'/ * static so zero filled * /'。可能会对删除静态的其余代码/数据产生影响 - 自动变量不会初始化为零,任何依赖于此类的代码都会受到损害。
另请注意,代码还有其他问题,与多线程无关。 'ftp'函数无法正确处理TCP的八位字节流特性,并错误地假设在默认字节流模式下调用read()时,将完全接收大于一个字节的消息。
即使对于非库代码,此代码也很糟糕,应该解雇作者:)