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POsend a file without waiting the reception of the whole file
 

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  1. POsend a file without waiting the reception of the whole file
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    <p>I have a Server that contact another Server in order to obtain a file and then send it to the Client. I have write this piece of code (C - Linux) but only the first 4 bytes arrive to the Client. Someone better than me can see the mistake? Thank you very much</p> <pre><code>int Recv_file (int s, int f, char *ptr, size_t maxlen){ int const TIMEOUT = 60; /* 60 seconds */ size_t n; ssize_t nread; ssize_t nsend; char c; fd_set cset; struct timeval tval; int x; for (n=1; n&lt;maxlen; n++) { FD_ZERO(&amp;cset); FD_SET(s, &amp;cset); tval.tv_sec = TIMEOUT; tval.tv_usec = 0; x = select(FD_SETSIZE, &amp;cset, NULL, NULL, &amp;tval); if (x==-1) { perror("select() failed"); return -1; /* -1 = close connection with the client */ } if (x&gt;0) { nread=recv(s, &amp;c, 1, 0); if (nread == 1) { *ptr++ = c; nsend = Send(f,&amp;c,1); if (nsend != 1) { return -1; /* close connection with the client */ } }else if (nread == 0){ *ptr = 0; return (-1); /* close connection with the client */ } else return (-1); /* close connection with the client */ }else{ printf("(It's been %d seconds and I have not received any response",TIMEOUT); close(s); return(-1); /* close connection with the client */ } } *ptr = 0; return (n); /* n == maxlen */ } </code></pre> <p>with:</p> <pre><code>int Send(int s, char *ptr, size_t nbytes){ size_t nleft; ssize_t nwritten; for (nleft=nbytes; nleft &gt; 0; ) { nwritten = send(s, ptr, nleft, 0); if (nwritten &lt;=0) return (nwritten); else { nleft -= nwritten; ptr += nwritten; } } return (nbytes - nleft); /* number of bytes sent */ } </code></pre> <p><em><strong>UPDATE:</em></strong></p> <p>While waiting for an answer I modified:</p> <p><code>nread=recv(s, &amp;c, 1, 0);</code> in <code>nread=recv(s, &amp;c, sizeof(c), 0);</code></p> <p>and</p> <p><code>Send(f,&amp;c,1);</code> in <code>Send(f,&amp;c,sizeof(c));</code></p> <p>But now I don't receive the last bytes of the file!</p> <p>Thank you again!</p>
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    1. USuser2467899
    1. USuser2467899
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      1. POsend a file without waiting the reception of the whole file
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    1. COFor `char c;` `1` is always equal to `sizeof(c)`.
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      1. POsend a file without waiting the reception of the whole file
      1. USalk
    2. COOh! Now I receive more bytes but not the last. So I have change n=1 in the for loop to n=0 but I obtain the same result
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      1. POsend a file without waiting the reception of the whole file
      1. USuser2467899
    3. COBTW: `if (x==-1) { perror("select() failed"); return -1; /* -1 = close connection with the client */ }` is too course. select() can return -1 with errno=EINTR for an interupted system call (such as the handling of a signal) In that case you should restart your selectloop, instead of quitting it. BTW2: reading/writing one char at a time is **extremely costly**. That would sum up to 3 syscalls per character.
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      1. POsend a file without waiting the reception of the whole file
      1. USwildplasser
 

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