The Linux Programming Interface: a linux and unix system Programming Handbook
A File-Server Application Using Message Queues
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- Điều hướng trang này:
- Figure 46-3
- Listing 46-7
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A File-Server Application Using Message Queues In this section, we describe a client-server application that uses one message queue per client. The application is a simple file server. The client sends a request message to the server’s message queue asking for the contents of a named file. The server responds by returning the file contents as a series of messages to the client’s private message queue. Figure 46-3 provides an overview of the application. Because the server performs no authentication of the client, any user that can run the client can obtain any of the files accessible to the server. A more sophisticated server would require some type of authentication from the client before serving the requested file. Figure 46-3: Client-server IPC using one message queue per client Common header file Listing 46-7 is the header file included by both the server and the client. This header defines the well-known key to be used for the server’s message queue Server MQ Client sends request to Server MQ (mtext includes ID of client queue) 2 3 Client reads response(s) 6 fork() msgg et( IPC_PRIV ATE, ...) 1 Client creates private queue Client MQ Server reads request 4 5 Server child sends response(s) Server creates child to handle request Client Server Server child 956 Chapter 46 ( SERVER_KEY ), and defines the formats of the messages to be passed between the cli- ent and the server. The requestMsg structure defines the format of the request sent from the client to the server. In this structure, the mtext component consists of two fields: the iden- tifier of the client’s message queue and the pathname of the file requested by the client. The constant REQ_MSG_SIZE equates to the combined size of these two fields and is used as the msgsz argument in calls to msgsnd() using this structure. The responseMsg structure defines the format of the response messages sent from the server back to the client. The mtype field is used in response messages to supply information about the message content, as defined by the RESP_MT_* constants. Listing 46-7: Header file for svmsg_file_server.c and svmsg_file_client.c ––––––––––––––––––––––––––––––––––––––––––––––––––––––– tải về 6.93 Mb. Chia sẻ với bạn bè của bạn:
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