From 5664bba1f343fb2f987d136527ffc742afc76f7e Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Wed, 18 Nov 2020 15:43:27 +0530
Subject: add q7: remote command executor

---
 q7/client.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
 q7/server.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 readme.txt  | 12 ++++++++++--
 3 files changed, 121 insertions(+), 2 deletions(-)
 create mode 100644 q7/client.c
 create mode 100644 q7/server.c

diff --git a/q7/client.c b/q7/client.c
new file mode 100644
index 0000000..32d89f3
--- /dev/null
+++ b/q7/client.c
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <unistd.h>
+#include <string.h>
+#include <arpa/inet.h>
+#include <string.h>
+
+int main(int argc, char* argv[]) { 
+    const char *server_name = "127.0.0.1";
+    int sockfd, connfd; 
+    struct sockaddr_in servaddr, cli; 
+
+    sockfd = socket(AF_INET, SOCK_STREAM, 0); 
+    servaddr.sin_family = AF_INET; 
+    inet_pton(AF_INET, server_name, &servaddr.sin_addr);
+
+    int port = atoi(argv[1]);
+    servaddr.sin_port = htons(port);
+
+    if((connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr))) == 0) {
+        printf("Connected to server!\n");
+        fflush(stdout);
+    } else {
+        printf("Invalid or busy server address\n");
+        fflush(stdout);
+        exit(0);
+    };
+
+    int cont = 0;
+    char *buf = malloc(1024);
+    char recevied[1024];
+    printf("Client input: ");
+    fgets(buf, 100, stdin);
+    while(strcmp(buf, "quit\n") != 0) {
+        send(sockfd, buf, 100, 0);
+        if ((cont = recv(sockfd, recevied, 1024, 0)) > 0) {
+            printf("Server response: %s\n", recevied);
+            fflush(stdout);
+            memset(recevied, 0, sizeof(recevied));
+        }
+        printf("Client input: ");
+        fgets(buf, 100, stdin);
+    };
+
+    close(sockfd); 
+}
diff --git a/q7/server.c b/q7/server.c
new file mode 100644
index 0000000..12df5bb
--- /dev/null
+++ b/q7/server.c
@@ -0,0 +1,62 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <unistd.h>
+#include <string.h>
+#include <arpa/inet.h>
+#include <wait.h>
+
+int main(int argc, char *argv[]) {
+    int sockfd, connfd; 
+    struct sockaddr_in servaddr, cli; 
+  
+    sockfd = socket(AF_INET, SOCK_STREAM, 0); 
+    servaddr.sin_family = AF_INET; 
+    servaddr.sin_addr.s_addr = htonl(INADDR_ANY); 
+
+    int port = atoi(argv[1]);
+    servaddr.sin_port = htons(port);
+  
+    bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
+  
+    listen(sockfd, 128);
+    printf("Server started at %s...\n", inet_ntoa(servaddr.sin_addr));
+    fflush(stdout);
+
+    while(1) {
+        socklen_t len = sizeof(cli);
+        connfd = accept(sockfd, (struct sockaddr *)&cli, &len);
+        int i = getpeername(connfd, (struct sockaddr*)&cli, &len);
+
+        printf("Client connected at port %d\n", htons(cli.sin_port));
+        int n;
+        char buf[100];
+        int pid;
+
+        if((pid=fork())==0){
+            close(sockfd);
+            while((n = recv(connfd, buf, 100, 0)) > 0) {
+                printf("Client message: %s\n", buf);
+                int pipes[2];
+                pipe(&pipes[0]);
+                if ((pid=fork()) == 0) {
+                    dup2(pipes[1], STDOUT_FILENO);
+                    close(pipes[0]);
+                    execl("/bin/sh", "sh", "-c", buf, (char *) NULL);
+                } else {
+                    close(pipes[1]);
+                    char cmd_output[1024];
+                    int cmd_size = read(pipes[0], cmd_output, sizeof(cmd_output));
+                    send(connfd, cmd_output, cmd_size, 0);
+                    wait(NULL);
+                }
+                fflush(stdout);
+            };
+            exit(0);
+        }
+        close(connfd);
+    }
+    return 0;
+}
diff --git a/readme.txt b/readme.txt
index 66b08b0..6aabaaf 100644
--- a/readme.txt
+++ b/readme.txt
@@ -1,6 +1,5 @@
 18CS54 - network programming and security
 ------------------------------------------------------------
-
 Q1: Write a networking program consisting of a client and
     server components. The client must request for a file by
     providing a file name, and the server must respond with the
@@ -10,8 +9,8 @@ Q1: Write a networking program consisting of a client and
 
 A1: https://u.peppe.rs/qt.png
 
-------------------------------------------------------------
 
+------------------------------------------------------------
 Q6: Write a networking program to demonstrate the following:
     a) Concurrent TCP server
     b) Iterative TCP server
@@ -21,5 +20,14 @@ A6: a) https://u.peppe.rs/E3.png
     b) https://u.peppe.rs/VA.png
     c) https://u.peppe.rs/ei.png
 
+
+------------------------------------------------------------
+Q7: Write a networking program that recieves a shell command
+    from a client and returns the output of the command to the
+    client.
+
+A7: https://u.peppe.rs/QD.png
+
+
 ------------------------------------------------------------
 mirror of git.peppe.rs/university/nps
-- 
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