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  1. PO
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    <p>It looks like the code writes and reads <code>struct msgbuf</code> incorrectly:</p> <pre><code>typedef struct msgbuf { int messageLength; int messageType; char messageText[MSGBUFFER_SIZE]; } Message_buf; // ... strcpy(client_MessageBuf.messageText,fileOperation); client_MessageBuf.messageLength=strlen(fileOperation); client_MessageBuf.messageType=1; if((writePIPE(writefd,&amp;client_MessageBuf))&lt;0) // .... int writePIPE(int fd, Message_buf *inputMessage){ printf("\n In write pipe message length :%d",inputMessage-&gt;messageLength); printf("\n In write pipe message Data :%s",inputMessage-&gt;messageText); ssize_t n=write(fd,inputMessage,inputMessage-&gt;messageLength); printf("\n Size :%d", n); return n; } </code></pre> <p>The above pieces that write <code>struct msgbuf</code> only write the first <code>messageLength</code> bytes of the structure which doesn't include the length of <code>messageLength</code> and <code>messageType</code> members, i.e. it truncates the object.</p> <p>When reading:</p> <pre><code>ssize_t readPIPE(int fd, Message_buf *outputMessage) { // ... if((n=read(fd,outputMessage,sizeof(outputMessage)))==0) </code></pre> <p>It reads only <code>sizeof(outputMessage)</code> bytes, which is the size of the pointer, not the object. Even if you fix it by changing it to <code>sizeof(*outputMessage)</code> that won't do enough, since that would expect to read the complete object whereas the writing piece truncates the object.</p> <p>A good start to fix it would be to split the message into two parts: header and payload. The header is a structure of a fixed size, e.g.:</p> <pre><code>typedef struct { int messageType; int payloadLength; } MessageHeader; </code></pre> <p>The payload is a variable-length part following the header. This way it would first write the entire header object into the pipe followed by <code>payloadLength</code> bytes of payload. When reading it would first read again the entire header and then read exactly <code>payloadLength</code> bytes.</p> <p>Also note, that <code>read()</code> and <code>write()</code> calls may read or write less then asked, so that case needs to be explicitly handled by keeping reading or writing until the exact number of bytes has been processed.</p>
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    1. POError writing and reading a structure from PIPE
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    1. USMaxim Egorushkin
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    1. COHi, i did fix the code and able to send and receive the data for the first time. But when i execute it second time, it give SIG_PIPE error. can you let me know what might be the reason for that and how to handle this
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      1. USuser1368949
    2. CO`SIGPIPE` means it writes to a pipe whose reader has disconnected.
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      1. USMaxim Egorushkin
 

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