C 中涉及套接字和客户端-服务器通信的程序问题

Question

我正在用 C 开发一个涉及客户端-服务器连接和双方通信的程序。

该程序涉及客户端向服务器端发送信件，服务器端收到信件。服务器然后在当前文件目录（在 linux 中）搜索以该字母开头的文件，并向客户端发送文件的字节数和文件的文本。

整个程序很长，对于作业，讲师已经做了很多代码，例如设置套接字和为操作的客户端创建整个程序。

对于服务器端，我必须为以下代码编写代码：

从传递的内存中获取文件描述符并转换它

-收到客户来信

-正在尝试打开当前目录

-遍历目录寻找以字母

开头的文件

-尝试打开文件并以网络字节序向客户端发送文件大小和文件字节数

-完成后关闭文件和目录

-错误检查：目录打不开，文件打不开，或者没有找到匹配的文件，都有错误检查语句

以下是我的注释代码

void*           handleClient    (void*  vPtr
                                )
{
  //  I.  Application validity check:

       int      fd              = *((int *) vPtr); 
     //casting vPtr to an int//

        free(vPtr);


//  II.  Handle the client:

        char buffer[BUFFER_LEN+1];
        read(fd, buffer, BUFFER_LEN+1);
        //read the letter into a buffer//

        const char* dirNamePtr = ".";
        DIR* dirPtr = opendir(dirNamePtr);
//   Open the current directory


        if (dirPtr == NULL)
        {
            int toSend = htonl(CANT_READ_DIR_CODE);
                write(fd,&toSend,sizeof(toSend));
                printf("Cannot read directory\n");
                return(NULL);
        }
// If current directory cannot be opened, it sends a error message in network // endian to the client

        struct dirent* entryPtr;
        char path[BUFFER_LEN];
        struct stat statBuffer;
//implements struct dirent to get info on the directory

//iterates through the directory
        while ((entryPtr=readdir(dirPtr)) != NULL)
        {


           stat(entryPtr->d_name, &statBuffer);
//puts in metaddata of the current directory into statbuffer


          if (!S_ISREG(statBuffer.st_mode))
                continue;
//if the entry is not a file, continue

// if the first letter of the file is not the character received from the //client, send an error mesage

          if(entryPtr->d_name[0]!=buffer[0])  {
                   int toSend2 = htonl(NO_MATCH_CODE);
                   write(fd,&toSend2,sizeof(toSend2));
                   printf("No matching file\n");
                   return(NULL);
               }


                int ab;
                int numRead;
                int numBytes;
                char buffer[BUFFER_LEN];
//open the file and send bytes of file and file size to client

            if (entryPtr->d_name[0]==buffer[0] &(S_ISREG(statBuffer.st_mode)))
                {

                        ab=open(entryPtr->d_name,O_RDONLY,0660);

                        if(ab<0) {
                                int toSend3 = htonl(CANT_READ_FILE_CODE);
                                write(fd,&toSend3, sizeof(toSend3));
                                printf("Cannot read <filename>\n");
                                return(NULL);
                                }

                        numBytes=htonl(statBuffer.st_size);
                        write(fd, &numBytes, sizeof(numBytes));

                        printf("Sending %s, %d bytes\n",entryPtr >d_name,statBuffer.st_size);


                while((numBytes=read(ab,buffer,BUFFER_LEN))>0)
                        {
                                printf("We read %d bytes\n", numBytes);
                                write(fd, buffer, numBytes);
                        }
//close the fiel

                       close(ab);

                }
                break;

//leave the loop





}

 //  III.  Finished:
//

closedir(dirPtr);

return(NULL);
}

我的代码可以编译，但当我尝试运行时没有将文件发送给客户端。我尝试了几个不同的字母，但对其中任何一个都不起作用。我不太清楚是什么问题导致我很难改正错误。

我不是要答案或任何东西，只是帮助看看我错在哪里。感谢您的帮助。

Answer 1

您关于何时发送与何时发送 no-file 状态的逻辑似乎有误。我认为它应该是这样的（公平的警告，我没有测试这个，甚至没有在基本语法检查之外编译它，但你应该明白这个想法）：

void* handleClient(void*  vPtr)
{
    //  I.  Application validity check:
    int fd = *((int *) vPtr);
    free(vPtr);

    //  II.  Handle the client:
    char buffer[BUFFER_LEN+1];
    read(fd, buffer, BUFFER_LEN+1);
    //read the letter into a buffer//

    const char* dirNamePtr = ".";
    DIR* dirPtr = opendir(dirNamePtr);
    //   Open the current directory

    if (dirPtr == NULL)
    {
        int toSend = htonl(CANT_READ_DIR_CODE);
        write(fd,&toSend,sizeof(toSend));
        printf("Cannot read directory\n");
        return(NULL);
    }

    struct dirent* entryPtr;
    char path[BUFFER_LEN];
    struct stat statBuffer;
    //implements struct dirent to get info on the directory

    //iterates through the directory
    while ((entryPtr=readdir(dirPtr)) != NULL)
    {
        stat(entryPtr->d_name, &statBuffer);
        //puts in metaddata of the current directory into statbuffer

        // if this isn't a regular file OR the first char doesn't match...
        if (!S_ISREG(statBuffer.st_mode) || entryPtr->d_name[0]!=buffer[0])
            continue;

        int ab;
        int numRead;
        int numBytes;
        char buffer[BUFFER_LEN];
        //open the file and send bytes of file and file size to client

        ab = open(entryPtr->d_name,O_RDONLY,0660);

        if(ab<0) {
            int toSend3 = htonl(CANT_READ_FILE_CODE);
            write(fd,&toSend3, sizeof(toSend3));
            printf("Cannot read <filename>\n");
            closedir(dirPtr);
            return(NULL);
        }

        numBytes=htonl(statBuffer.st_size);
        write(fd, &numBytes, sizeof(numBytes));

        printf("Sending %s, %d bytes\n",entryPtr >d_name,statBuffer.st_size);
        while((numBytes=read(ab,buffer,BUFFER_LEN))>0)
        {
            printf("We read %d bytes\n", numBytes);
            write(fd, buffer, numBytes);
        }

        //close the file and leave
        close(ab);
        break;
    }

    // if this is NULL it means we dind't send anything. we break the loop
    //  when a file to send it discovered.
    if (entryPtr == NULL)
    {
        printf("No matching file\n");
        int toSend2 = htonl(NO_MATCH_CODE);
        write(fd, &toSend2, sizeof(toSend2));
    }

    //  III.  Finished:
    closedir(dirPtr);

    return(NULL);
}

C 中涉及套接字和客户端-服务器通信的程序问题

Issue with program involving sockets and client-server communication in C

c

sockets

directory

client

server