I am working on User Interface for a linux script. I need a code that can intera

Question

I am working on User Interface for a linux script. I need a code that can interact with that linux script as client-server program. Forexample a code that can get a response from the linux script. A friend of mine told me that we can use ubuntu for a best result. My linux script is called master. Master shares jobs between computers to be excecute. The purpose of my user interface is to contact the master to find out if a job is completed or incompleted. After contacting the master, it will say job complete or job incomplete.

Explanation / Answer

Code that can interact with that linux script as client-server program. Socket - Server Code: #include #include #include #include #include #include #include #include #include #include int main(int argc, char *argv[]) { int listenfd = 0, connfd = 0; struct sockaddr_in serv_addr; char sendBuff[1025]; time_t ticks; listenfd = socket(AF_INET, SOCK_STREAM, 0); memset(&serv_addr, '0', sizeof(serv_addr)); memset(sendBuff, '0', sizeof(sendBuff)); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); serv_addr.sin_port = htons(5000); bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)); listen(listenfd, 10); while(1) { connfd = accept(listenfd, (struct sockaddr*)NULL, NULL); ticks = time(NULL); snprintf(sendBuff, sizeof(sendBuff), "%.24s ", ctime(&ticks)); write(connfd, sendBuff, strlen(sendBuff)); close(connfd); sleep(1); } } Explanation: The call to the function ‘socket()’ creates an UN-named socket inside the kernel and returns an integer known as socket descriptor. This function takes domain/family as its first argument. For Internet family of IPv4 addresses we use AF_INET. The second argument ‘SOCK_STREAM’ specifies that the transport layer protocol that we want should be reliable ie it should have acknowledgement techniques. For example : TCP The third argument is generally left zero to let the kernel decide the default protocol to use for this connection. For connection oriented reliable connections, the default protocol used is TCP. The call to the function ‘bind()’ assigns the details specified in the structure ‘serv_addr’ to the socket created in the step above. The details include, the family/domain, the interface to listen on(in case the system has multiple interfaces to network) and the port on which the server will wait for the client requests to come. The call to the function ‘listen()’ with second argument as ’10’ specifies maximum number of client connections that server will queue for this listening socket. After the call to listen(), this socket becomes a fully functional listening socket. In the call to accept(), the server is put to sleep and when for an incoming client request, the three way TCP handshake* is complete, the function accept () wakes up and returns the socket descriptor representing the client socket. The call to accept() is run in an infinite loop so that the server is always running and the delay or sleep of 1 sec ensures that this server does not eat up all of your CPU processing. As soon as server gets a request from client, it prepares the date and time and writes on the client socket through the descriptor returned by accept(). Socket - Client Code: #include #include #include #include #include #include #include #include #include #include int main(int argc, char *argv[]) { int sockfd = 0, n = 0; char recvBuff[1024]; struct sockaddr_in serv_addr; if(argc != 2) { printf(" Usage: %s ",argv[0]); return 1; } memset(recvBuff, '0',sizeof(recvBuff)); if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) { printf(" Error : Could not create socket "); return 1; } memset(&serv_addr, '0', sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_port = htons(5000); if(inet_pton(AF_INET, argv[1], &serv_addr.sin_addr) 0) { recvBuff[n] = 0; if(fputs(recvBuff, stdout) == EOF) { printf(" Error : Fputs error "); } } if(n < 0) { printf(" Read error "); } return 0; } Explanation: We see that here also, a socket is created through call to socket() function. Information like IP address of the remote host and its port is bundled up in a structure and a call to function connect() is made which tries to connect this socket with the socket (IP address and port) of the remote host. Note that here we have not bind our client socket on a particular port as client generally use port assigned by kernel as client can have its socket associated with any port but In case of server it has to be a well known socket, so known servers bind to a specific port like HTTP server runs on port 80 etc while there is no such restrictions on clients. Once the sockets are connected, the server sends the data (date+time) on clients socket through clients socket descriptor and client can read it through normal read call on the its socket descriptor. Output: $ ./newsc 127.0.0.1 Thu Apr 13 08:53:14 2017

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