From 425966de0eb7a729913329457a1850c54b7404e2 Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Wed, 24 Nov 2021 20:57:23 +0100
Subject: tsdwl: add exam

---
 Year_3/TSDWL/ex_20140428/socket.c | 123 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 Year_3/TSDWL/ex_20140428/socket.c

diff --git a/Year_3/TSDWL/ex_20140428/socket.c b/Year_3/TSDWL/ex_20140428/socket.c
new file mode 100644
index 0000000..b82d6cb
--- /dev/null
+++ b/Year_3/TSDWL/ex_20140428/socket.c
@@ -0,0 +1,123 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <time.h>
+#include <unistd.h>
+
+#define PORT 3233
+
+void
+ban(char* ban_list[], char* address, int* index, int *ban_size)
+{
+    if (*index > 4) {
+        *index = 0;
+    }
+
+    if (*ban_size < 5) (*ban_size)++;
+
+    strcpy(ban_list[*index], address);
+
+    (*index)++;
+}
+
+int
+is_banned_addr(char* ban_list[], int n, char* address)
+{
+    int i;
+
+    for (i = 0; i < n; ++i) {
+        if (strcmp(ban_list[i], address) == 0)
+            return 1;
+    }
+
+    return 0;
+}
+
+int
+main(int argc, char* argv[])
+{
+    int sockfd, clientfd;
+    struct sockaddr_in addr;
+    socklen_t addrlen;
+    char buffer[12];
+    int nbytes;
+    char last_not_valid[15];
+    time_t now_time;
+    struct tm* now;
+    char* addr_str;
+    int i;
+    int ban_i;
+    int ban_size;
+    char* ban_list[5];
+
+    for (i = 0; i < 5; ++i) {
+        ban_list[i] = malloc(sizeof(char) * 15);
+    }
+
+    if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
+        perror("socket");
+        exit(1);
+    }
+
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(atoi(argv[1])); // TODO: change with PORT
+    addr.sin_addr.s_addr = INADDR_ANY;
+
+    addrlen = sizeof(addr);
+
+    if (bind(sockfd, (struct sockaddr*)&addr, addrlen) == -1) {
+        perror("bind");
+        exit(1);
+    }
+
+    if (listen(sockfd, 1) == -1) {
+        perror("listen");
+        exit(1);
+    }
+
+    ban_i = ban_size = 0;
+    while (1) {
+        if ((clientfd = accept(sockfd, (struct sockaddr*)&addr, &addrlen)) == -1) {
+            perror("accept");
+            continue;
+        }
+
+        if ((nbytes = read(clientfd, buffer, sizeof(buffer))) == -1) {
+            perror("read");
+            goto clientclear;
+        }
+
+        buffer[nbytes-1] = 0;
+        addr_str = inet_ntoa(addr.sin_addr);
+
+        if (is_banned_addr(ban_list, ban_size, addr_str)) {
+            sprintf(buffer, "BANNED\n");
+        } else if (strncmp(buffer, "TIME", 4) == 0) {
+            time(&now_time);
+            now = gmtime(&now_time);
+            sprintf(buffer, "%d:%d:%d UTC\n", now->tm_hour, now->tm_min, now->tm_sec);
+            memset(last_not_valid, 15, 0);
+        } else {
+            sprintf(buffer, "N/A\n");
+            if (strcmp(last_not_valid, addr_str) == 0) {
+                ban(ban_list, addr_str, &ban_i, &ban_size);
+                sprintf(buffer, "BANNED\n");
+            } else {
+                strcpy(last_not_valid, addr_str);
+            }
+        }
+        write(clientfd, buffer, strlen(buffer));
+
+clientclear:
+        close(clientfd);
+    }
+
+    for (i = 0; i < 5; ++i) {
+        free(ban_list[i]);
+    }
+
+    close(sockfd);
+    return 0;
+}
-- 
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