Network  Programming-TCP/UDP Sockets

Bare Minimum Clients/Servers:

udpServer & udpClient

tcpServer & tcpClient

Comprehensive Clients/Servers:

UDPServer & UDPClient

TCPServer & TCPClient

---

Bare Minimum Clients/Servers

Each server (upd or tcp):

ü Creates a server socket,

ü Binds it to a fixed port (10203),

ü Receives a message from a client and displays it.

Each client (udp or tcp):

ü Creates a client socket.

ü Sends "Hi" repeatedly out of this socket to the server.

---

udp Server & Client

ê udpServer.c

 
#include "def"
main()
{ int sd;
 struct sockaddr_in server; 
 char buf[512];
 int rc;


 server.sin_family = AF_INET;
 server.sin_addr.s_addr = htonl(INADDR_ANY);
 server.sin_port = htons(12345);




 sd = socket (AF_INET,SOCK_DGRAM,0);
 bind ( sd, (SA *) &server, sizeof(server));
 for(;;){
  rc = recv (sd, buf, sizeof(buf), 0);
 buf[rc]= (char) NULL;
 printf("Received: %s\n", buf);
 }
}




 
Usage example:




% udpServer0
 

ê udpClient.c

#include "def"
main(..)
{

  int sd; 
 struct sockaddr_in server; 
 struct hostent *hp, *gethostbyname();
 
 sd = socket (AF_INET,SOCK_DGRAM,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);
 
   for (;;) {
  sendto(sd,"HI",2,0,(SA *)&server, sizeof(server));
  sleep(2);
  }

}

Usage example:

% udpClient0 localhost

---

tcp Server & Client

ê 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);
 close (sd); 
 
 for(;;) {

  cc = recv(psd,buf,sizeof(buf, 0) ; 
  if (cc == 0) exit (0);
  buf[cc] = NULL;
  printf("message received: %s\n", buf); 

 }

}




 
Usage example:




% tcpServer0
 




 
 
ê tcpClient.c

#include "def"

main(..) {

 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 ); 
   sleep(2); 
 }

}

Usage example:

% tcpClient0 localhost

---

Comprehensive Clients/Servers

Each server (upd or tcp):

ü Creates a server socket,

ü Binds it to a  port.

The port can be specified using either:

· Argument to the program (e.g., argv[1]), or

· Chosen by the system (0 to indicate that choice) and displayed after bind, using getsockname.

ü Receives a message from a client and displays:

· The received message,

· The ip/name of the client,  and

· The port number of the client.

ü Sends (echo back) the received message to its sender.

Each Client (upd or tcp):

ü Creates a client socket and contacts the server using two arguments: <host> <port>

ü Sends to the server a message typed by the user.

ü Receives from the server the echoed message and displays it along with the ip/name and port number of the server.

---

êUDPServer.c

main( ...) 
{
 ..... 
 
 /* get Host information, NAME and INET ADDRESS */ 
 gethostname(ThisHost, MAXHOSTNAME); 
 printf("UDPServer1 running at:%s\n", ThisHost);
 hp = gethostbyname(ThisHost);
 bcopy ( hp->h_addr, &(server.sin_addr), hp->h_length);
 printf("(UDPServer1 INET ADDRESS is: %s )\n",
  inet_ntoa(server.sin_addr)); 
 
 /* Construct name of socket to send to. */ 
 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_DGRAM,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));




 
 /* get data from clients and send it back */
 for(;;){
 fromlen = sizeof(from); 
 rc = recvfrom(sd,buf,sizeof(buf,0,(SA*)&from,&fromlen);

  if (rc > 0){
 buf[rc]=NULL;
 printf("Received: %s\n", buf);
 printf("From %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); 
 sendto(sd, buf, rc, 0, (SA *) &from, sizeof(from));
 }
 }
}
 

Usage example:

% UDPSever1
% UDPSever1 10203

---

ê UDPClient.c

 
 
main(... ) 
 
{ ..... 
 
 /*get UDPClient1 Host information,NAME and INET ADDRESS */
 
 gethostname(ThisHost, MAXHOSTNAME);
 printf("UDPClient1 running at: %s\n", ThisHost);
 hp = gethostbyname(ThisHost));
 bcopy ( hp->h_addr, &(server.sin_addr), hp->h_length);
 printf("(UDPClient1 INET ADDRESS is: %s )\n", 
 inet_ntoa(server.sin_addr));
 
 
 /*get UDPServer1 Host information, NAME & INET ADDRESS*/
 if ( (hp = gethostbyname(argv[1])) == NULL ) {
 addr.sin_addr.s_addr = inet_addr(argv[1]); 
 hp = gethostbyaddr((char *)&addr.sin_addr.s_addr, 
 sizeof(addr.sin_addr.s_addr),AF_INET));
 }
 printf("UDPServer1 running at: %s\n", hp->h_name); 
 bcopy ( hp->h_addr, &(server.sin_addr), hp->h_length); 
 printf("(UDPServer1 INET ADDRESS is: %s )\n",
 inet_ntoa(server.sin_addr));
 
 
 /* Construct name of socket to send to. */
 server.sin_family = AF_INET;
 server.sin_port = htons(atoi(argv[2]));
 
 
 /* Create socket on which to send and receive */
 sd = socket (AF_INET,SOCK_DGRAM,0); 
 
 
 /* get data from USER, send it SERVER, 
 receive it from SERVER, display it back to USER */
 for(;;) {
 printf("Type anything followed by RETURN, to exit type CTRL-D \n");
 rc=read(0,buf, sizeof(buf));
 if (rc == 0) break;
 
 sendto(sd, buf, rc, 0, (SA *)&server, sizeof(server)); 
  
 fromlen= sizeof(from);
 cc=recvfrom(sd, rbuf, sizeof(rbuf), 0,(SA *) &from, &fromlen));
 
 printf(" Received: %s", rbuf);
 printf(" from %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); 
  }
 printf ("EOF... exit\n");
 close(sd); 
 exit (0);

 }
 
Usage example:

% UDPClient1 localhost 2222

---

ê TCPServer.c

main( ... ) {

.....

/*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:

% TCPServer1

% TCPServer1 10203

---

ê 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));
bcopy ( hp->h_addr, &(server.sin_addr), hp->h_length);
printf(" (TCP/Cleint INET ADDRESS is: %s )\n", inet_ntoa(server.sin_addr));

/* get TCPServer1 Host information, NAME and INET ADDRESS */
if ( (hp = gethostbyname(argv[1])) == NULL ) {

addr.sin_addr.s_addr = inet_addr(argv[1]);
hp = gethostbyaddr((char *) &addr.sin_addr.s_addr,
sizeof(addr.sin_addr.s_addr),AF_INET);

}
printf("TCP/Server running at host NAME: %s\n", hp->h_name);
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 to send to. */
server.sin_family = AF_INET;
server.sin_port = htons(atoi(argv[2]));

/* Create socket on which to send and receive */
sd = socket (AF_INET,SOCK_STREAM,0);

/** Connect to TCPServer1 */
connect(sd, (SA *) &server, sizeof(server));
fromlen = sizeof(from);
getpeername(sd,(SA *)&from,&fromlen);
printf("Connected to TCPServer1: ");
printf("%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);
childpid = fork();
if (childpid == 0) {
GetUserInput();
}

/* receive it from SERVER, display it back to USER */
for(;;) {

recv(sd, rbuf, sizeof(rbuf), 0)) ;
printf(" Received: %s", rbuf);

}

}

/* 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