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    <p>Some comments in no particular order:</p> <ul> <li><p>You're passing up the opportunity to know exact errors too often:</p> <pre><code>if(listen(sockfd,BACKLOG) == -1) { printf("ERROR: Failed to listen Port %d.\n", PORT); return (0); } </code></pre> <p>This block should definitely include a <code>perror("listen")</code> or something similar. Always include <code>perror()</code> or <code>strerror()</code> in every error handling block when the error details will be reported via <code>errno</code>. Having exact failure reasons will save you hours when programming and will save you and your users hours when things don't work as expected in the future.</p></li> <li><p>Your error handling needs some further standardizing:</p> <pre><code>if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1 ) { printf("ERROR: Failed to obtain Socket Descriptor.\n"); return (0); } </code></pre> <p>This should <em>not</em> <code>return 0</code> because that will signal to the shell that the program ran to completion without error. You should <code>return 1</code> (or use <code>EXIT_SUCCESS</code> and <code>EXIT_FAILURE</code>) to signal an abnormal exit.</p> <pre><code> else printf("[Server] Server has got connected from %s.\n", inet_ntoa(addr_remote.sin_addr)); /*Receive File from Client */ </code></pre> <p>In this preceding block you've gotten an error condition but continue executing anyway. That's a quick way to get very undesirable behavior. This should either re-start the main server loop or exit the child process or something similar. (Depends if you keep the multi-process server.)</p> <pre><code>if(!fork()) { </code></pre> <p>The preceding block forgot to account for <code>fork()</code> <em>failing</em>. <code>fork()</code> can, and does fail -- especially in shared hosting environments common at universities -- so you should be prepared for the full, complicated <em>three</em> possible return values from <code>fork()</code>: failure, child, parent.</p></li> <li><p>It appears you're using <code>fork()</code> indiscriminately; your client and server are both very simple and the way they are designed to run means they <em>cannot</em> be used to service multiple clients simultaneously. You should probably stick to exactly one process for each, at least until the algorithm is perfectly debugged and you figure out some way to run multiple clients simultaneously. I expect this is the source of the problem you're encountering now.</p></li> <li><p>You need to use functions to encapsulate details; write a function to connect to the server, a function to send the file, a function to write the file, etc. Write a function to handle the complicated partial writes. (I especially recommend stealing the <code>writen</code> function from the <a href="http://www.apuebook.com/" rel="noreferrer">Advanced Programming in the Unix Environment</a> book's source code. File <code>lib/writen.c</code>.) If you write the functions correctly you can re-use them in both the client and server. (Something like placing them in <code>utils.c</code> and compiling the programs like <code>gcc -o server server.c utils.c</code>.)</p> <p>Having smaller functions that each do one thing will allow you to focus on smaller amounts of code at a time <em>and</em> write little tests for each that will help you narrow down which sections of code still need improvement.</p></li> </ul>
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    1. COHey, thank you for the tips. I don't really like programming, that's probably why i'm not very good at it. Anyway i want to get better so i'll try to follow your tips. If you don't mind could you elaborate the part of "It appears you're using fork() indiscriminately...."? I don't think i'm serving multiple clients, i call ./client just once and it should go on by iteself. And how can i stick to one process? Thanks again! PS: It's 4 in the morning here so if you answer is possible i won't answer back, don't take it personally!
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    2. COThink about what `fork()` does -- it gives you a copy of the program. Why does your client need a copy of itself? Why does your server need a copy of itself? You could probably remove the `fork()` entirely from both programs without ill effects. (It'd make _reasoning_ about the programs far easier.)
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    3. COI'll start by reminding you that i found this code around. i didn't write it and i didn't think too much about it (this to say that what i'm saying is probably gonna be wrong), but how can i get to the child if i don't use the fork()? For what i know (and i know is not much) when the server accept a connection it creates a new socket (so a new process) to manage the client connectiong so i use the result of the fork to get to that. Or maybe i'm just mistaken, i don't really know.
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