我正在尝试使用POSIX API构建多线程Web服务器。这是到目前为止我得到的：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <pthread.h>
const char CONTENTDIR[]="./contentdir" ; // this is the directory where keep all the files for requests
pthread_mutex_t mutex;
void error(const char *msg)
{
perror(msg);
exit(1);
}
struct user_input
{
int sockfd;
int thread_NO;
int buffer_size;
pthread_t *thread_pool;
int newsockfd;
}input;
void httpWorker(int *);// This function will handle request
char * fType(char *);
char * responseHeader(int, char *);// function that builds response header
void *thread_pool(void *); //This function is called in main() function to create thread pool and create scheduling thread
void *sched_thread(void *); //This function is called in main_thread() function to call worker threads by using for loop
int main(int argc, char *argv[])
{
pthread_t main_thread;
int sockfd, newsockfd, portno;
struct user_input *input = (struct user_input *)malloc(sizeof(struct user_input));
input->thread_NO = atoi(argv[2]);//gathering user input of thread number
input->buffer_size = atoi(argv[3]);//same for buffer size
socklen_t clilen;
struct sockaddr_in serv_addr, cli_addr;
if (argc < 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
error("ERROR on binding");
listen(sockfd, input->buffer_size);
while(1)
{
input->sockfd = sockfd;
pthread_create(&main_thread, NULL, (void *)thread_pool, (void *)input);
pthread_join(main_thread, NULL);
}
close(sockfd);
return 0;
}
void *thread_pool(void *input)
{
int worker_id;//index for creating thread pool
//Casting info from struct argument passed from main()
struct user_input *input_args = (struct user_input *)input;
input_args->sockfd = ((struct user_input *)input)->sockfd;
int thread_NO = ((struct user_input *)input)->thread_NO;
//Getting ready to create thread pool and scheduling thread
pthread_t thread_pool[thread_NO];
pthread_t main_thread2;
input_args->thread_pool = &thread_pool[thread_NO];
//thread pool creating
for(worker_id = 0; worker_id < sizeof(thread_NO); worker_id++)
{
input_args->thread_pool[worker_id] = worker_id;
}
//creating scheduling thread
pthread_create(&main_thread2, NULL, sched_thread, (void *)input_args);
pthread_join(main_thread2, NULL);
}
void *sched_thread(void *input)
{
int newsockfd;
//gathering info from struct passed from main_thread()
struct user_input *input_args = (struct user_input *)input;
int sockfd = ((struct user_input *)input)->sockfd;
input_args->buffer_size = ((struct user_input *)input)->buffer_size;
socklen_t clilen;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
pthread_t *worker_thread = input_args->thread_pool;
while(1)
{
clilen = sizeof(cli_addr);
newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
error("ERROR on accept");
for(int i = 0; i < input_args->buffer_size; i++)
{
pthread_create(&worker_thread[i], NULL, (void *)httpWorker, &newsockfd);
}
for(int i = 0; i < input_args->buffer_size; i++)
{
pthread_detach(worker_thread[i]);
}
}
pthread_exit(NULL);
}
void httpWorker(int *sockfd)//sockfd contains all the information
{
int newsockfd = *sockfd;// create a local variable for sockfd
char buffer[256];// we will read the data in this buffer
char *token;// local variable to split the request to get the filename
bzero(buffer,256);// intialize the buffer data to zero
char fileName[50];
char homedir[50];
char * type;
strcpy(homedir,CONTENTDIR);// directory where files are stored.
char *respHeader; //response header
// start reading the message from incoming conenction
if (read(newsockfd,buffer,255) < 0)
error("ERROR reading from socket");
//get the requested file part of the request
token = strtok(buffer, " ");// split string into token seperated by " "
token = strtok(NULL, " ");// in this go we read the file name that needs to be sent
strcpy(fileName,token);
// get the complete filename
if(strcmp(fileName,"/")==0) // if filename is not provided then we will send index.html
strcpy(fileName,strcat(homedir,"/index.html"));
else
strcpy(fileName,strcat(homedir,fileName));
type = fType(fileName);// get file type
//open file and ready to send
FILE *fp;
int file_exist=1;
fp=fopen(fileName, "r");
if (fp==NULL) file_exist=0;
respHeader = responseHeader(file_exist,type);
if ((send(newsockfd, respHeader,strlen(respHeader), 0) == -1) || (send(newsockfd,"\r\n", strlen("\r\n"), 0) == -1))
perror("Failed to send bytes to client");
free(respHeader);// free the allocated memory (note: the memory is allocated in responseheader function)
if (file_exist)
{
char filechar[1];
while((filechar[0]=fgetc(fp))!=EOF)
{
if(send(newsockfd,filechar,sizeof(char),0) == -1) perror("Failed to send bytes to client");
}
}
else
{
if (send(newsockfd,"<html> <HEAD><TITLE>404 Not Found</TITLE></HEAD><BODY>Not Found</BODY></html> \r\n", 100, 0) == -1)
perror("Failed to send bytes to client");
}
close(newsockfd);
}
// function below find the file type of the file requested
char * fType(char * fileName){
char * type;
char * filetype = strrchr(fileName,'.');// This returns a pointer to the first occurrence of some character in the string
if((strcmp(filetype,".htm"))==0 || (strcmp(filetype,".html"))==0)
type="text/html";
else if((strcmp(filetype,".jpg"))==0)
type="image/jpeg";
else if(strcmp(filetype,".gif")==0)
type="image/gif";
else if(strcmp(filetype,".txt")==0)
type="text/plain";
else
type="application/octet-stream";
return type;
}
//buildresponseheader
char * responseHeader(int filestatus, char * type){
char statuscontent[256] = "HTTP/1.0";
if(filestatus==1){
strcat(statuscontent," 200 OK\r\n");
strcat(statuscontent,"Content-Type: ");
strcat(statuscontent,type);
strcat(statuscontent,"\r\n");
}
else {
strcat(statuscontent,"404 Not Found\r\n");
//send a blank line to indicate the end of the header lines
strcat(statuscontent,"Content-Type: ");
strcat(statuscontent,"NONE\r\n");
}
char * returnheader =malloc(strlen(statuscontent)+1);
strcpy(returnheader,statuscontent);
return returnheader;
}
我通过在thread_pool函数中创建pthread_t数组来构建“线程池”。而sched_thread将把接受的文件描述符传递给每个工作线程。 Failed to send bytes to client: Bad file descriptor说，bash在运行时会返回一长串错误消息。 Failed to send bytes to client: Socket operation on non-socket出现在前两行。
我想知道是否是因为我没有使用互斥体来锁定每个工作线程，还是使用pthread API是否有任何错误？在我在ubuntu WSL下测试时，添加pthread之前的原始服务器程序可以正常工作。
有什么建议吗？
答案 0 :(得分：1)
您不能像
那样将对堆栈上变量的引用传递给新线程pthread_create(&worker_thread[i], NULL, (void *)httpWorker, &newsockfd);
newsockfd存储在另一个线程的堆栈中，并且当您的新线程开始运行时，newsockfd所在的堆栈帧可能甚至不再存在或包含不同的堆栈帧或内存位置已由其他堆栈变量重用。
传递给线程的数据通常必须是静态内存或已分配的内存，决不能是堆栈内存，除非可以保证在新线程读取该值之前，堆栈帧一定会保持冻结状态（因此，阻止创建者线程，直到新线程通知它已经复制了值）。
在传递input时您做得正确
pthread_create(&main_thread, NULL, (void *)thread_pool, (void *)input);
在这里您显式分配内存以传递给线程。
顺便说一句，对void *的强制转换是没有意义的； void *仅表示“任何指针”（不是真的，但您可以假装确实如此），因此可以为void *参数传递任何指针，而无需强制转换。