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Network Programming-TCP Sockets (lecture programs)
Bare Minimum Clients/Servers
Each server:
¾ Creates a server socket , ¾ Binds it to a fixed port (10203), ¾ Receives a message from a client and displays it.
Each client (udp or tcp):
¾ Creates a client socket , ¾ Sends "Hi" repeatedly out of this socket to the server.
tcp Server and Client
tcpServer.c
#include "def" main() { int sd, psd; struct sockaddr_in name; char buf[1024]; int cc;
sd = socket (AF_INET,SOCK_STREAM,0);
name.sin_family = AF_INET; name.sin_addr.s_addr = htonl(INADDR_ANY); name.sin_port = htons(10203);
bind( sd, (SA *) &name, sizeof(name) );
listen(sd,1);
psd = accept(sd, 0, 0);
for(;;) { cc=recv(psd,buf,sizeof(buf), 0) ; if (cc == 0) exit (0); buf[cc] = NULL; printf("message received: %s\n", buf); } }
Usage example:
% tcpServer
tcpClient.c
#include "def"
main(argc, argv ) int argc; char *argv[];
{ int sd; struct sockaddr_in server; struct hostent *hp, *gethostbyname();
sd = socket (AF_INET,SOCK_STREAM,0);
server.sin_family = AF_INET; hp = gethostbyname(argv[1]); bcopy ( hp->h_addr, &(server.sin_addr.s_addr), hp-
h_length); server.sin_port = htons(10203);
connect(sd, (SA *) &server, sizeof(server));
for (;;) { send(sd, "HI", 2, 0 ); printf("sent HI\n"); sleep(2); } }
/get TCPServer1 Host information: NAME and INET ADDRESS/
gethostname(ThisHost, MAXHOSTNAME); printf("TCP/Server running at host NAME: %s\n", ThisHost); hp = gethostbyname(ThisHost)); bcopy ( hp->h_addr, &(server.sin_addr), hp->h_length); printf(" (TCP/Server INET ADDRESS is: %s )\n", inet_ntoa(server.sin_addr));
/* Construct name of socket / server.sin_family = AF_INET; server.sin_addr.s_addr = htonl(INADDR_ANY); if (argc == 1) server.sin_port = htons(0); else { server.sin_port = htons(atoi(argv[1])); } / Create socket on which to send and receive */ sd = socket (AF_INET,SOCK_STREAM,0); bind( sd, (SA *) &server, sizeof(server);
/* get port information and prints it out */ length = sizeof(server); getsockname (sd, (SA *)&server,&length); printf("Server Port is: %d\n", ntohs(server.sin_port));
/* accept TCP connections & fork a process to serve each client */ listen(sd,4); fromlen = sizeof(from); for(;;){ psd = accept(sd, (SA *)&from, &fromlen); childpid = fork(); if ( childpid == 0) { close (sd); EchoServe(psd, from); } else{ printf("My new child pid is %d\n", childpid); close(psd); } } }
EchoServe(psd, from) int psd; struct sockaddr_in from; { .... /* print client information */ printf("Serving %s:%d\n",inet_ntoa(from.sin_addr),
ntohs(from.sin_port));
hp = gethostbyaddr((char *) &from.sin_addr.s_addr, sizeof(from.sin_addr.s_addr),AF_INET));
printf("(Name is : %s)\n", hp->h_name);
/* get data from clients and send it back */ for(;;){ rc=recv(psd, buf, sizeof(buf), 0); if (rc > 0){ buf[rc]=NULL; printf("Received: %s\n", buf); printf("From TCP/Client: %s:%d\n", inet_ntoa(from.sin_addr), ntohs(from.sin_port)); printf("(Name is : %s)\n", hp->h_name); send(psd, buf, rc, 0); }else { printf("Disconnected..\n"); close (psd); exit(0); } } }
Usage example:
% TCPServer % TCPServer1 10101
TCPClient.c
main( ..) { ....
/*get TCPClient1 Host information, NAME and INET ADDRESS */ gethostname(ThisHost, MAXHOSTNAME); printf("TCP/Cleint running at host NAME: %s\n", ThisHost); hp = gethostbyname(ThisHost));
/* get data from USER, send it SERVER */
GetUserInput() { for(;;) { printf("Type anything followed by RETURN, or type CTRL-D to exit\n"); rc=read(0,buf, sizeof(buf)); if (rc == 0) break; send(sd, buf, rc, 0); } printf ("EOF... exit\n"); close(sd); kill(getppid(), 9); exit (0); }
Usage example:
% TCPClient1 localhost 10101
