Programming Forums > Application Development > C++

Brent · Jul 1st, 2005, 6:23 PM

whenever i make a network program it always says "failed recv()" or "failed send()", and i can never get it to work. any suggestions?

here's the server:

(Toggle Plain Text)

#include<winsock.h>
#include<iostream.h>
#include<string.h>
#pragma comment(lib,"wsock32.lib")

SOCKET server;
SOCKET client;

int main()
{
	WORD sockversion;
	WSADATA wsaData;
	int net;
	
	sockversion=MAKEWORD(1,1);
	WSAStartup(sockversion,&wsaData);
	
	server=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP);
	if(server==INVALID_SOCKET)
	{
		cout<<"invalid socket\n";
		WSACleanup();
	}
	
	sockaddr_in sin;
	sin.sin_family=PF_INET;
	sin.sin_port=htons(8888);
	sin.sin_addr.s_addr=INADDR_ANY;
	
	net=bind(server,(LPSOCKADDR)&sin,sizeof(sin));
	if(net==SOCKET_ERROR)
	{
		cout<<"failed bind()";
		WSACleanup();
	}
	
	net=listen(server,4);
	if(net==SOCKET_ERROR)
	{
		cout<<"failed listen\n";
		WSACleanup();
	}
	
	client=accept(server,NULL,NULL);
	if(client==INVALID_SOCKET)
	{
		cout<<"failed accept\n";
		WSACleanup();
	}
	
	while(true);
	{
		char rdata[5000];
		char data[5000];
		
		net=recv(client,rdata,strlen(rdata),0);
		if(net==SOCKET_ERROR)
		{
			cout<<"failed recv()\n";
			WSACleanup();
		}
		
		cout<<"===================================\n";
		cout<<"\n";
		cout<<">>"<<rdata<<'\n';
		cout<<"<you said>"<<data<<'\n';
		cout<<"\n";
		cout<<"===================================\n";
		cout<<">> ";
		cin.get(data,4999);
		cin.ignore(80,'\n');
		
		net=send(server,data,strlen(data),0);
		if(net==SOCKET_ERROR)
		{
			cout<<"failed send\n";
			WSACleanup();
		}
	}
	
	WSACleanup();
	closesocket(server);
	closesocket(client);
	return 0;
}

here's the client

(Toggle Plain Text)

#include<winsock.h>
#include<iostream.h>
#include<string.h>
#pragma comment(lib,"wsock32.lib")

SOCKET server;
SOCKET client;

int main()
{
	WORD sockversion;
	WSADATA wsaData;
	int net;
	
	sockversion=MAKEWORD(1,1);
	WSAStartup(sockversion,&wsaData);
	
	client=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP);
	if(client==INVALID_SOCKET)
	{
		cout<<"invalid socket\n";
		WSACleanup();
	}
	
	sockaddr_in sin;
	sin.sin_familt=PF_INET;
	sin.sin_port=htons(8888);
	sin.sin_addr.s_addr=inet_addr("127.0.0.1");
	
	net=connect(client,(LPSOCKADDR)&sin,sizeof(sin));
	if(net==SOCKET_ERROR)
	{
		cout<<"failed to connect to server\n";
		WSACleanup();
	}
	
	
	while(true);
	{
		char rdata[5000];
		char data[5000];
		
		net=send(server,data,strlen(data),0);
		if(net==SOCKET_ERROR)
		{
			cout<<"failed send\n";
			WSACleanup();
		}
		
		cout<<"===================================\n";
		cout<<"\n";
		cout<<">>"<<rdata<<'\n';
		cout<<"<you said>"<<data<<'\n';
		cout<<"\n";
		cout<<"===================================\n";
		cout<<">> ";
		cin.get(data,4999);
		cin.ignore(80,'\n');
		
		net=recv(client,rdata,strlen(rdata),0);
		if(net==SOCKET_ERROR)
		{
			cout<<"failed recv()\n";
			WSACleanup();
		}
	}
	
	WSACleanup();
	closesocket(server);
	closesocket(client);
	return 0;
}

thanks in advance

DaWei · Jul 1st, 2005, 7:25 PM

These are HTML pages; they eat whitespace. Please put your code in tags to preserve its indentation. Otherwise, it's uglier than my ex-mother-in-law, and I won't read it. The "How to Post...." thread in the C forum is a good read, also.

Mjordan2nd · Jul 1st, 2005, 8:54 PM

Code tags added for ease on the eyes.

The Dark · Jul 2nd, 2005, 9:26 PM

In this line in the server

(Toggle Plain Text)

		net=recv(client,rdata,strlen(rdata),0);

Don't use strlen, use sizeof - you want to be able to fill out your entire buffer, not just up to the first zero byte of the random data that is in there.

In this line in the client

(Toggle Plain Text)

		net=send(server,data,strlen(data),0);

You haven't put anything in data yet, so it contains random garbage, which might be a null in the first byte. This would mean you are attempting to send nothing, which probably would cause an error.

You need to either send the zero byte from the client to the server, to indicate end of string, or use the received length to add a zero byte to the end of the characters you are putting in rdata on the server, otherwise your string is unterminated.

Brent · Jul 12th, 2005, 6:10 PM

Quote:

You need to either send the zero byte from the client to the server, to indicate end of string, or use the received length to add a zero byte to the end of the characters you are putting in rdata on the server, otherwise your string is unterminated.

could you give me an example please...

Brent · Jul 12th, 2005, 6:13 PM

Could someone tell me how to use the "select() function", or how to implement it in my program?

DaWei · Jul 12th, 2005, 7:02 PM

Go here in Beej's guide. I recommend you bookmark this or download a copy of the PDF version or something. Google is your friend if Beej falls through.

Jul 1st, 2005, 6:23 PM	#1
Brent Highly Adaptive Penguin Join Date: May 2005 Location: United States Posts: 249 Rep Power: 4	problem with network application whenever i make a network program it always says "failed recv()" or "failed send()", and i can never get it to work. any suggestions? here's the server: (Toggle Plain Text) #include<winsock.h> #include<iostream.h> #include<string.h> #pragma comment(lib,"wsock32.lib") SOCKET server; SOCKET client; int main() { WORD sockversion; WSADATA wsaData; int net; sockversion=MAKEWORD(1,1); WSAStartup(sockversion,&wsaData); server=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP); if(server==INVALID_SOCKET) { cout<<"invalid socket\n"; WSACleanup(); } sockaddr_in sin; sin.sin_family=PF_INET; sin.sin_port=htons(8888); sin.sin_addr.s_addr=INADDR_ANY; net=bind(server,(LPSOCKADDR)&sin,sizeof(sin)); if(net==SOCKET_ERROR) { cout<<"failed bind()"; WSACleanup(); } net=listen(server,4); if(net==SOCKET_ERROR) { cout<<"failed listen\n"; WSACleanup(); } client=accept(server,NULL,NULL); if(client==INVALID_SOCKET) { cout<<"failed accept\n"; WSACleanup(); } while(true); { char rdata[5000]; char data[5000]; net=recv(client,rdata,strlen(rdata),0); if(net==SOCKET_ERROR) { cout<<"failed recv()\n"; WSACleanup(); } cout<<"===================================\n"; cout<<"\n"; cout<<">>"<<rdata<<'\n'; cout<<"<you said>"<<data<<'\n'; cout<<"\n"; cout<<"===================================\n"; cout<<">> "; cin.get(data,4999); cin.ignore(80,'\n'); net=send(server,data,strlen(data),0); if(net==SOCKET_ERROR) { cout<<"failed send\n"; WSACleanup(); } } WSACleanup(); closesocket(server); closesocket(client); return 0; } #include<winsock.h> #include<iostream.h> #include<string.h> #pragma comment(lib,"wsock32.lib") SOCKET server; SOCKET client; int main() { WORD sockversion; WSADATA wsaData; int net; sockversion=MAKEWORD(1,1); WSAStartup(sockversion,&wsaData); server=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP); if(server==INVALID_SOCKET) { cout<<"invalid socket\n"; WSACleanup(); } sockaddr_in sin; sin.sin_family=PF_INET; sin.sin_port=htons(8888); sin.sin_addr.s_addr=INADDR_ANY; net=bind(server,(LPSOCKADDR)&sin,sizeof(sin)); if(net==SOCKET_ERROR) { cout<<"failed bind()"; WSACleanup(); } net=listen(server,4); if(net==SOCKET_ERROR) { cout<<"failed listen\n"; WSACleanup(); } client=accept(server,NULL,NULL); if(client==INVALID_SOCKET) { cout<<"failed accept\n"; WSACleanup(); } while(true); { char rdata[5000]; char data[5000]; net=recv(client,rdata,strlen(rdata),0); if(net==SOCKET_ERROR) { cout<<"failed recv()\n"; WSACleanup(); } cout<<"===================================\n"; cout<<"\n"; cout<<">>"<<rdata<<'\n'; cout<<"<you said>"<<data<<'\n'; cout<<"\n"; cout<<"===================================\n"; cout<<">> "; cin.get(data,4999); cin.ignore(80,'\n'); net=send(server,data,strlen(data),0); if(net==SOCKET_ERROR) { cout<<"failed send\n"; WSACleanup(); } } WSACleanup(); closesocket(server); closesocket(client); return 0; } here's the client (Toggle Plain Text) #include<winsock.h> #include<iostream.h> #include<string.h> #pragma comment(lib,"wsock32.lib") SOCKET server; SOCKET client; int main() { WORD sockversion; WSADATA wsaData; int net; sockversion=MAKEWORD(1,1); WSAStartup(sockversion,&wsaData); client=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP); if(client==INVALID_SOCKET) { cout<<"invalid socket\n"; WSACleanup(); } sockaddr_in sin; sin.sin_familt=PF_INET; sin.sin_port=htons(8888); sin.sin_addr.s_addr=inet_addr("127.0.0.1"); net=connect(client,(LPSOCKADDR)&sin,sizeof(sin)); if(net==SOCKET_ERROR) { cout<<"failed to connect to server\n"; WSACleanup(); } while(true); { char rdata[5000]; char data[5000]; net=send(server,data,strlen(data),0); if(net==SOCKET_ERROR) { cout<<"failed send\n"; WSACleanup(); } cout<<"===================================\n"; cout<<"\n"; cout<<">>"<<rdata<<'\n'; cout<<"<you said>"<<data<<'\n'; cout<<"\n"; cout<<"===================================\n"; cout<<">> "; cin.get(data,4999); cin.ignore(80,'\n'); net=recv(client,rdata,strlen(rdata),0); if(net==SOCKET_ERROR) { cout<<"failed recv()\n"; WSACleanup(); } } WSACleanup(); closesocket(server); closesocket(client); return 0; } #include<winsock.h> #include<iostream.h> #include<string.h> #pragma comment(lib,"wsock32.lib") SOCKET server; SOCKET client; int main() { WORD sockversion; WSADATA wsaData; int net; sockversion=MAKEWORD(1,1); WSAStartup(sockversion,&wsaData); client=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP); if(client==INVALID_SOCKET) { cout<<"invalid socket\n"; WSACleanup(); } sockaddr_in sin; sin.sin_familt=PF_INET; sin.sin_port=htons(8888); sin.sin_addr.s_addr=inet_addr("127.0.0.1"); net=connect(client,(LPSOCKADDR)&sin,sizeof(sin)); if(net==SOCKET_ERROR) { cout<<"failed to connect to server\n"; WSACleanup(); } while(true); { char rdata[5000]; char data[5000]; net=send(server,data,strlen(data),0); if(net==SOCKET_ERROR) { cout<<"failed send\n"; WSACleanup(); } cout<<"===================================\n"; cout<<"\n"; cout<<">>"<<rdata<<'\n'; cout<<"<you said>"<<data<<'\n'; cout<<"\n"; cout<<"===================================\n"; cout<<">> "; cin.get(data,4999); cin.ignore(80,'\n'); net=recv(client,rdata,strlen(rdata),0); if(net==SOCKET_ERROR) { cout<<"failed recv()\n"; WSACleanup(); } } WSACleanup(); closesocket(server); closesocket(client); return 0; } thanks in advance Last edited by Mjordan2nd; Jul 1st, 2005 at 8:53 PM.

Jul 1st, 2005, 7:25 PM	#2
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	These are HTML pages; they eat whitespace. Please put your code in tags to preserve its indentation. Otherwise, it's uglier than my ex-mother-in-law, and I won't read it. The "How to Post...." thread in the C forum is a good read, also. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jul 1st, 2005, 8:54 PM	#3
Mjordan2nd The Supreme Ruler Join Date: May 2004 Location: Houston Posts: 1,476 Rep Power: 6	Code tags added for ease on the eyes. __________________ "Every gun that is made, every warship launched, every rocket signifies, in the final sense, a theft from those who hunger and are not fed, from those who are cold and are not clothed. The world in arms is not spending money alone. It is spending the sweat of its laborers, the genius of its scientists, the hopes of its children." - Dwight D. Eisenhower

Jul 2nd, 2005, 9:26 PM	#4
The Dark Expert Programmer Join Date: Jun 2005 Posts: 816 Rep Power: 4	In this line in the server (Toggle Plain Text) net=recv(client,rdata,strlen(rdata),0); net=recv(client,rdata,strlen(rdata),0); Don't use strlen, use sizeof - you want to be able to fill out your entire buffer, not just up to the first zero byte of the random data that is in there. In this line in the client (Toggle Plain Text) net=send(server,data,strlen(data),0); net=send(server,data,strlen(data),0); You haven't put anything in data yet, so it contains random garbage, which might be a null in the first byte. This would mean you are attempting to send nothing, which probably would cause an error. You need to either send the zero byte from the client to the server, to indicate end of string, or use the received length to add a zero byte to the end of the characters you are putting in rdata on the server, otherwise your string is unterminated.

Jul 12th, 2005, 7:02 PM	#7
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Go here in Beej's guide. I recommend you bookmark this or download a copy of the PDF version or something. Google is your friend if Beej falls through. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jul 12th, 2005, 6:13 PM	#6
Brent Highly Adaptive Penguin Join Date: May 2005 Location: United States Posts: 249 Rep Power: 4	Could someone tell me how to use the "select() function", or how to implement it in my program?

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Programming Forums > Application Development > C++

problem with network application