udp connection problem

[saee]

hello group,
i'm trying to send a socket over udp. i'm doing it on same machine with loopback address. i wrote a server code n a client code. when i run them both, there should be a connection when i send text from client to server. client window shows sent complete n server window says waiting for connection that means recvfrom() is hanged or blocked. it does not go beyond recvfrom(). i tried connect() also from client. no luck.
my pseudo code is,

//client.c
while(1){
create server socket
create client socket
s = socket(AF_INET, SOCK_DGRAM, 0);
bind() //client socket
sendto(s,buf,10,0,server,sizeof());
}


//server.c

creat server socket
s= socket()
bind(server)
while(1){
"waiting for connection"
recvfrom(s,buf,10,0,client,length);
}

please tell wer am i doing wrong.
n one more,
i have such a code for TCp also. it works fine with loopback addr. two windows on same machine talk to each other. but it does not work with network addr. like if i replace 127.0.0.1 with 192.168.1.85 it gives error.

[horace1]

not sure why you have bind() in the client

s = socket(AF_INET, SOCK_DGRAM, 0);
bind() //client socket
sendto(s,buf,10,0,server,sizeof());

unless you are going to send datagrams both ways only the receiver uses bind()

for examples of TCP and UCP clients and servers see
http://www.linuxhowtos.org/C_C++/socket.htm

[saee]

i tried without bind() also. it does not work..

[horace1]

could you post your code?

[saee]

sure. thanks for ur reply.

//cleint.cpp
#define TAR_IPAddress "192.128.1.85"

int main()
{
WORD wVersionRequested;
WSADATA wsaData;
SOCKADDR_IN server, client; //Socket address information
SOCKET s;
struct hostent *hp;
int err, b;
int bytesSent, bytesRecv;
char buf[100] = "hi hello", k[2], recvbuf[100] ;
char host_name[156]; //host name of this machine
int addr_len = sizeof(struct sockaddr);



//--- INITIALIZATION -----------------------------------
wVersionRequested = MAKEWORD( 1, 1 );
err = WSAStartup( wVersionRequested, &wsaData );

if ( err != 0 ) {
printf("WSAStartup error %ld", WSAGetLastError());
WSACleanup();
return false;
}
//---------------------------------------------------------


//---- creat a server struct.--------
server.sin_family = AF_INET; // address family Internet
server.sin_port = htons (SERVER_PORT); //Port to connect on
server.sin_addr.s_addr = inet_addr (IPAddress); //Target IP

//--------------------------------------------------------

//---- creat a client struct---------------------------------
client.sin_family = AF_INET; // address family Internet
client.sin_port = htons (0); //Port to connect on
client.sin_addr.s_addr = inet_addr(IPAddress); //host IP
//--------------------------------------------------------


while(1) {
// ---- create SOCKET--------------------------------------
s = socket (AF_INET, SOCK_DGRAM, 0); //Create socket
if (s == INVALID_SOCKET)
{
printf("socket error %ld" , WSAGetLastError() );
_getch();
WSACleanup();
return false; //Couldn't create the socket
}
//---------------------------------------------------------

//---- SEND bytes -------------------------------------------

printf("trans buf:('q' to quit)\n");
gets(buf);
if ((strcmp(buf , "q") == 0) || strcmp(buf , "Q") == 0)
break;
bytesSent = sendto (s, buf, 10, 0, (struct sockaddr*) &server, sizeof(sockaddr));
if(bytesSent < 0 ){
printf("sendto fails with : %ld\n ", WSAGetLastError());
// _getch();
WSACleanup();
}
else
printf("bytes sent : %d\n" ,bytesSent );
//-------------------------------------------------------------------------


// WSACleanup();
}
return 0;
}

//server.cpp

#define SERVER_PORT 1167
#define BUF_SIZE 4096 // block transfer size
#define QUEUE_SIZE 10
#define IPAddress "127.0.0.1" // Local to the system - Loop back address


int main()
{
int b, on = 1;
char recvbuf[10] = { }, buf[10];
SOCKET s;
struct sockaddr_in server, client; // holds IP address
WORD wVersionRequested;
WSADATA wsaData;
int err;
int bytesRecv, bytesSent;
int addr_len = sizeof(struct sockaddr);


//--- INITIALIZATION -----------------------------------
wVersionRequested = MAKEWORD( 1, 1 );
err = WSAStartup( wVersionRequested, &wsaData );

if ( err != 0 ) {
printf("WSAStartup error %ld", WSAGetLastError());
WSACleanup();
return false;
}
//---------------------------------------------------------

//------------ server socket ----------------------------
server.sin_addr.s_addr = inet_addr (IPAddress); //Target IP
server.sin_family = AF_INET; // address family Internet
server.sin_port = htons (SERVER_PORT); //Port to connect on
//-----------------------------------------------------------------

while (1) {

// ---- create SOCKET--------------------------------------
s = socket(AF_INET, SOCK_DGRAM, 0); //0 specifies to use appropriate protocol according to request
if (s < 0) {
printf("socket error %ld",WSAGetLastError() );
WSACleanup();
return false;
}
//--------------------------------------------------------


//---- BIND socket ----------------------------------------
b = bind(s, (struct sockaddr *) &server, sizeof(sockaddr));
if (b == -1) {
printf("bind error\n");
printf("socket error %ld",WSAGetLastError() );
WSACleanup();
_getch();
return false;
}

//----------------------------------------------------------

printf("waiting for a connection\n");

//-----------receive bytes -------------------------------------------------------------

bytesRecv = recvfrom(s, recvbuf, 10, 0, (struct sockaddr * )&client, &addr_len );
if(bytesRecv < 0){
printf("recvfrom error : %ld", WSAGetLastError());
WSACleanup();
}

printf("connection ");
if ( bytesRecv == 0 || bytesRecv == WSAECONNRESET ) {
printf( "Closed.\n");
WSACleanup();
}
else printf("accepted\n");
printf("received from: %s %d\n ", inet_ntoa(client.sin_addr), ntohs(client.sin_port));

printf( " Bytes Recv: %s \n ", recvbuf );

//-------------------------------------------------------------


}
WSACleanup();

return 0;
}

[horace1]

your server attempted to bind after receiving a message so I modified the server slightly

#include <iostream>
#include <winsock2.h>
 
 
using namespace std;
//server.cpp
 
#define SERVER_PORT 1167
#define BUF_SIZE 4096 // block transfer size
#define QUEUE_SIZE 10
#define IPAddress "127.0.0.1" // Local to the system - Loop back address
 
 
int main()
{
int b, on = 1;
char recvbuf[10] = { }, buf[10];
SOCKET s;
struct sockaddr_in server, client; // holds IP address
WORD wVersionRequested;
WSADATA wsaData;
int err;
int bytesRecv, bytesSent;
int addr_len = sizeof(struct sockaddr);
 
 
//--- INITIALIZATION -----------------------------------
wVersionRequested = MAKEWORD( 1, 1 );
err = WSAStartup( wVersionRequested, &wsaData );
 
if ( err != 0 ) {
printf("WSAStartup error %ld", WSAGetLastError());
WSACleanup();
return false;
}
//---------------------------------------------------------
 
//------------ server socket ----------------------------
server.sin_addr.s_addr = inet_addr (IPAddress); //Target IP
server.sin_family = AF_INET; // address family Internet
server.sin_port = htons (SERVER_PORT); //Port to connect on
//-----------------------------------------------------------------
 
while (1) {
 
// ---- create SOCKET--------------------------------------
s = socket(AF_INET, SOCK_DGRAM, 0); //0 specifies to use appropriate protocol according to request
if (s < 0) {
printf("socket error %ld",WSAGetLastError() );
WSACleanup();
return false;
}
//--------------------------------------------------------
 
 
//---- BIND socket ----------------------------------------
b = bind(s, (struct sockaddr *) &server, sizeof(sockaddr));
if (b == -1) {
printf("bind error\n");
printf("socket error %ld",WSAGetLastError() );
WSACleanup();
getchar();
return false;
}
 
//----------------------------------------------------------
while(1)
{
printf("waiting for data\n");
 
//-----------receive bytes -------------------------------------------------------------
 
bytesRecv = recvfrom(s, recvbuf, 10, 0, (struct sockaddr * )&client, &addr_len );
if(bytesRecv < 0){
printf("recvfrom error : %ld", WSAGetLastError());
WSACleanup();
}
 
printf("connection ");
if ( bytesRecv == 0 || bytesRecv == WSAECONNRESET ) {
printf( "Closed.\n");
WSACleanup();
}
else printf("accepted\n");
printf("received from: %s %d\n ", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
 
printf( " Bytes Recv: %s \n ", recvbuf );
}
//-------------------------------------------------------------
 
 
}
WSACleanup();
 
return 0;
}
 

the client I made a few modifications so it would compile on my machine

#include <iostream>
#include <winsock2.h>
 
 
using namespace std;
//cleint.cpp
#define TAR_IPAddress "192.128.1.85"
 
#define SERVER_PORT 1167
#define BUF_SIZE 4096 // block transfer size
#define QUEUE_SIZE 10
#define IPAddress "127.0.0.1" // Local to the system - Loop back address
 
 
int main()
{
WORD wVersionRequested;
WSADATA wsaData;
SOCKADDR_IN server, client; //Socket address information
SOCKET s;
struct hostent *hp;
int err, b;
int bytesSent, bytesRecv;
char buf[100] = "hi hello", k[2], recvbuf[100] ;
char host_name[156]; //host name of this machine
int addr_len = sizeof(struct sockaddr);
 
 
 
//--- INITIALIZATION -----------------------------------
wVersionRequested = MAKEWORD( 1, 1 );
err = WSAStartup( wVersionRequested, &wsaData );
 
if ( err != 0 ) {
printf("WSAStartup error %ld", WSAGetLastError());
WSACleanup();
return false;
}
//---------------------------------------------------------
 
 
//---- creat a server struct.--------
server.sin_family = AF_INET; // address family Internet
server.sin_port = htons (SERVER_PORT); //Port to connect on
server.sin_addr.s_addr = inet_addr (IPAddress); //Target IP
 
//--------------------------------------------------------
 
//---- creat a client struct---------------------------------
client.sin_family = AF_INET; // address family Internet
client.sin_port = htons (0); //Port to connect on
client.sin_addr.s_addr = inet_addr(IPAddress); //host IP
//--------------------------------------------------------
 
 
while(1) {
// ---- create SOCKET--------------------------------------
s = socket (AF_INET, SOCK_DGRAM, 0); //Create socket
if (s == INVALID_SOCKET)
{
printf("socket error %ld" , WSAGetLastError() );
getchar();
WSACleanup();
return false; //Couldn't create the socket
}
//---------------------------------------------------------
 
//---- SEND bytes -------------------------------------------
 
printf("trans buf:('q' to quit)\n");
gets(buf);
if ((strcmp(buf , "q") == 0) || strcmp(buf , "Q") == 0)
break;
bytesSent = sendto (s, buf, 10, 0, (struct sockaddr*) &server, sizeof(sockaddr));
if(bytesSent < 0 ){
printf("sendto fails with : %ld\n ", WSAGetLastError());
// _getch();
WSACleanup();
}
else
printf("bytes sent : %d\n" ,bytesSent );
//-------------------------------------------------------------------------
 
 
// WSACleanup();
}
return 0;
}
 

it then ran OK - the client output was

trans buf:('q' to quit)
hello 
bytes sent : 10
trans buf:('q' to quit)
this is message 2
bytes sent : 10
trans buf:('q' to quit)
message3
bytes sent : 10
trans buf:('q' to quit)
goodbye
bytes sent : 10
trans buf:('q' to quit)
q
 

and the server

waiting for data
connection accepted
received from: 127.0.0.1 1200
  Bytes Recv: hello 
 waiting for data
connection accepted
received from: 127.0.0.1 1202
  Bytes Recv: this is meÿÿ)NÃwBNÃwPÍ@ 
 waiting for data
connection accepted
received from: 127.0.0.1 1204
  Bytes Recv: message3 
 waiting for data
connection accepted
received from: 127.0.0.1 1206
  Bytes Recv: goodbye 
 waiting for data
 

clearly still a problem with buffer lengths
this only works with the client using localhost 127.0.0.1 not sure why

[saee]

Thank you. It works fine.

[saee]

horace1, can you please tell me why is it not working with network ip address?
Instead of loop back address i will have give another machines IP address. n it shoulld communicate. but server is not responding. it gets hung on Recvfrom().