518 Lecture Notes Week 12

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1 518 Lecture Notes Week 12 (November 16, 2014) 1/ Lecture Notes Week 12 1 Topics TCP/IP C programing for sockets 2 TCP/IP The socket call (socket_create.c) int main(int argc, char *argv[]) int socket_desc; socket_desc = socket(af_inet, SOCK_STREAM, 0); fprintf(stderr, "Could not create socket\n"); printf("created a socked\n"); Notes: A socket is one endpoint of a bidirectional communications channel. The first argument is domain: usually AF_INET, AF_INET6, AF_UNIX or AF_LOCAL. (We usually use AF_INET based on the IPv4 protocol.) The second argument is the socket type: usually SOCK_STREAM (TCP reliable communication) or SOC_DGRAM (UDP unreliable communication). We always set the third agrument to 0. (Other values indicate unusual protocols.)

2 518 Lecture Notes Week 12 (November 16, 2014) 2/13 connect.c int main(int argc, char *argv[]) int socket_desc; struct sockaddr_in server; socket_desc = socket(af_inet, SOCK_STREAM, 0); server.sin_addr.s_addr = inet_addr(" "); //google.com printf("inet address: %08X\n", server.sin_addr.s_addr); server.sin_port = htons(80); printf("port: %04x\n", server.sin_port); //Connect to remote server if (connect(socket_desc, (struct sockaddr *)&server, sizeof(server)) < 0) puts("connect error"); puts("connected"); connect_send.c

3 518 Lecture Notes Week 12 (November 16, 2014) 3/13 #include<string.h> //strlen int main(int argc, char *argv[]) int socket_desc; struct sockaddr_in server; char *message; socket_desc = socket(af_inet, SOCK_STREAM, 0); server.sin_addr.s_addr = inet_addr(" "); server.sin_port = htons(80); //Connect to remote server if (connect(socket_desc,(struct sockaddr *)&server,sizeof(server))<0) puts("connect error"); puts("connected\n"); //Send some data message = "GET / HTTP/1.1\r\n\r\n"; if( send(socket_desc, message, strlen(message), 0) < 0) puts("send failed"); puts("data Send\n");

4 518 Lecture Notes Week 12 (November 16, 2014) 4/13 connect_send_receive.c #include<string.h> //strlen int main(int argc, char *argv[]) int socket_desc; struct sockaddr_in server; char *message, server_reply[2000]; socket_desc = socket(af_inet, SOCK_STREAM, 0); server.sin_addr.s_addr = inet_addr(" "); server.sin_port = htons(80); //Connect to remote server if(connect(socket_desc, (struct sockaddr *)&server, sizeof(server))<0) puts("connect error"); puts("connected\n"); //Send some data message = "GET / HTTP/1.1\r\n\r\n"; if( send(socket_desc, message, strlen(message), 0) < 0) puts("send failed"); puts("data Send\n"); //Receive a reply from the server if( recv(socket_desc, server_reply, 2000, 0) < 0) puts("recv failed"); puts("reply received\n");

5 518 Lecture Notes Week 12 (November 16, 2014) 5/13 puts(server_reply); get_host_by_name.c //printf #include<string.h> //strcpy #include<netdb.h> //hostent #include<arpa/inet.h> int main(int argc, char *argv[]) char *hostname = "google.ca"; char ip[100]; struct hostent *he; struct in_addr **addr_list; int i; if ((he = gethostbyname(hostname)) == NULL) //gethostbyname failed herror("gethostbyname"); //Cast the h_addr_list to in_addr, //since h_addr_list also has the ip address in long format only addr_list = (struct in_addr **) he->h_addr_list; for (i = 0; addr_list[i]!= NULL; i++) strcpy(ip, inet_ntoa(*addr_list[i])); printf("i: %d, ip: %s\n", i, ip); //Return the first one; strcpy(ip, inet_ntoa(*addr_list[0])); printf("%s resolved to : %s", hostname, ip);

6 518 Lecture Notes Week 12 (November 16, 2014) 6/13 accept.c A simple server int main(int argc, char *argv[]) int socket_desc, new_socket, c; struct sockaddr_in server, client; socket_desc = socket(af_inet, SOCK_STREAM, 0); //Prepare the sockaddr_in structure server.sin_addr.s_addr = INADDR_ANY; server.sin_port = htons( 8888 ); //Bind if( bind(socket_desc,(struct sockaddr *)&server, sizeof(server)) < 0) puts("bind failed"); puts("bind done"); //Listen listen(socket_desc, 3); //Accept and incoming connection puts("waiting for incoming connections..."); c = sizeof(struct sockaddr_in); new_socket = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c); if (new_socket<0) perror("accept failed"); puts("connection accepted");

7 518 Lecture Notes Week 12 (November 16, 2014) 7/13 accept_hello.c #include<string.h> //strlen #include<unistd.h> //write int main(int argc, char *argv[]) int socket_desc, new_socket, c; struct sockaddr_in server, client; char *message; socket_desc = socket(af_inet, SOCK_STREAM, 0); //Prepare the sockaddr_in structure server.sin_addr.s_addr = INADDR_ANY; server.sin_port = htons(8888); //Bind if( bind(socket_desc,(struct sockaddr *)&server, sizeof(server)) < 0) puts("bind failed"); puts("bind done"); //Listen listen(socket_desc, 3); //Accept and incoming connection puts("waiting for incoming connections..."); c = sizeof(struct sockaddr_in); new_socket = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c);

8 518 Lecture Notes Week 12 (November 16, 2014) 8/13 if (new_socket<0) perror("accept failed"); puts("connection accepted"); //Reply to the client message = "Hello Client, I'm busy...bye\n"; write(new_socket, message, strlen(message)); live_server.c #include<string.h> //strlen #include<unistd.h> //write int main(int argc, char *argv[]) int socket_desc, new_socket, c; struct sockaddr_in server, client; char *message; socket_desc = socket(af_inet, SOCK_STREAM, 0); //Prepare the sockaddr_in structure server.sin_addr.s_addr = INADDR_ANY; server.sin_port = htons(8888); //Bind if( bind(socket_desc,(struct sockaddr *)&server, sizeof(server)) < 0) puts("bind failed");

9 518 Lecture Notes Week 12 (November 16, 2014) 9/13 puts("bind done"); //Listen listen(socket_desc, 3); //Accept and incoming connection puts("waiting for incoming connections..."); c = sizeof(struct sockaddr_in); while((new_socket = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c))) puts("connection accepted"); //Reply to the client message = "Hello Client, still busy...bye\n"; write(new_socket, message, strlen(message)); if (new_socket<0) perror("accept failed"); simple_echo.c /* */ C socket server example, handles multiple clients using threads #include<string.h> //strlen #include<stdlib.h> //strlen #include<unistd.h> //write #include<pthread.h> //for threading, link with lpthread #include <ctype.h> //the thread function

10 518 Lecture Notes Week 12 (November 16, 2014) 10/13 void *connection_handler(void *); int main(int argc, char *argv[]) int socket_desc, client_sock, c, *new_sock; struct sockaddr_in server, client; socket_desc = socket(af_inet, SOCK_STREAM, 0); puts("socket created"); //Prepare the sockaddr_in structure server.sin_addr.s_addr = INADDR_ANY; server.sin_port = htons( 8888 ); //Bind if( bind(socket_desc,(struct sockaddr *)&server, sizeof(server)) < 0) //print the error message perror("bind failed. Error"); puts("bind done"); //Listen listen(socket_desc, 3); //Accept and incoming connection puts("waiting for incoming connections..."); c = sizeof(struct sockaddr_in); while( (client_sock = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c)) ) puts("connection accepted"); pthread_t sniffer_thread; new_sock = malloc(1); *new_sock = client_sock; if( pthread_create(&sniffer_thread, NULL, connection_handler, (void*) new_sock) < 0) perror("could not create thread");

11 518 Lecture Notes Week 12 (November 16, 2014) 11/13 //Now join the thread, so that we dont terminate before the thread // pthread_join( sniffer_thread, NULL); puts("handler assigned"); if (client_sock < 0) perror("accept failed"); /* * This will handle connection for each client * */ void *connection_handler(void *socket_desc) //Get the socket descriptor int sock = *(int*)socket_desc; int read_size; char *message, client_message[2000]; char * cp; //Send some messages to the client message = "I am your connection handler\n"; write(sock, message, strlen(message)); message = "Now type something and I shall echo it in UPPERCASE\n"; write(sock, message, strlen(message)); //Receive a message from client while( (read_size = recv(sock, client_message, 2000, 0)) > 0 ) //Convert message to uppercase for(cp = client_message; *cp; cp++) *cp = toupper(*cp); //Send the message back to client write(sock, client_message, strlen(client_message)); if(read_size == 0) puts("client disconnected");

12 518 Lecture Notes Week 12 (November 16, 2014) 12/13 fflush(stdout); else if(read_size == -1) perror("recv failed"); //Free the socket pointer free(socket_desc); echo_client.c /* C ECHO client example using sockets */ //printf #include<string.h> //strlen //socket int main(int argc, char *argv[]) int sock; struct sockaddr_in server; char message[1000], server_reply[2000]; sock = socket(af_inet, SOCK_STREAM, 0); if (sock == -1) puts("socket created"); server.sin_addr.s_addr = inet_addr(" "); server.sin_port = htons(8888); //Connect to remote server if (connect(sock, (struct sockaddr *)&server, sizeof(server)) < 0) perror("connect failed. Error");

13 518 Lecture Notes Week 12 (November 16, 2014) 13/13 puts("connected\n"); //keep communicating with server while(1) printf("enter message : "); scanf("%s", message); //Send some data write(sock, message, strlen(message)); //Receive a reply from the server if( recv(sock, server_reply, 2000, 0) < 0) puts("recv failed"); break; puts("server reply :"); puts(server_reply); close(sock);

// Embedded Systems // BeagleBoard-XM. // Author : Jose Goncalves //

// Embedded Systems // BeagleBoard-XM // Author : Jose Goncalves // jose.braga.pt@gmail.com // Teacher : Nuno Peixoto // University : IPCA // 17.03.2014 #include #include #include