c++: Simple TCP server not accepting data from client - c++

Question

I have to create a simple tcp server that accepts some commands from the server and responds to them in a certain way. I started with just a simple thing in which server accepts anything from client as command and responds "In response to your command" to client 10 times as answer. But even this is not working. Please help.
server.cpp
# include <string.h>
# include <unistd.h>
# include <stdio.h>
# include <netdb.h>
# include <sys/types.h>
# include <sys/stat.h>
# include <sys/socket.h>
# include <netinet/in.h>
# include <iostream>
# include <fstream>
# include <string.h>
# include <stdlib.h>
# include <string>
# include <pthread.h>
# include <dirent.h>
using namespace std;
void *task1(void *);
static int connFd;
int main(int argc, char* argv[])
{
int pId, portNo, listenFd;
socklen_t len; //store size of the address
bool loop = false;
struct sockaddr_in svrAdd, clntAdd;
pthread_t threadA[3];
if (argc < 2)
{
cerr << "Syntax : ./server <port>" << endl;
return 0;
}
portNo = atoi(argv[1]);
if((portNo > 65535) || (portNo < 2000))
{
cerr << "Please enter a port number between 2000 - 65535" << endl;
return 0;
}
//create socket
listenFd = socket(AF_INET, SOCK_STREAM, 0);
if(listenFd < 0)
{
cerr << "Cannot open socket" << endl;
return 0;
}
bzero((char*) &svrAdd, sizeof(svrAdd));
svrAdd.sin_family = AF_INET;
svrAdd.sin_addr.s_addr = INADDR_ANY;
svrAdd.sin_port = htons(portNo);
//bind socket
if(bind(listenFd, (struct sockaddr *)&svrAdd, sizeof(svrAdd)) < 0)
{
cerr << "Cannot bind" << endl;
return 0;
}
listen(listenFd, 5);
len = sizeof(clntAdd);
int noThread = 0;
while (noThread < 3)
{
cout << "Listening" << endl;
//this is where client connects. svr will hang in this mode until client conn
connFd = accept(listenFd, (struct sockaddr *)&clntAdd, &len);
if (connFd < 0)
{
cerr << "Cannot accept connection" << endl;
return 0;
}
else
{
cout << "Connection successful" << endl;
}
pthread_create(&threadA[noThread], NULL, task1, NULL);
noThread++;
}
for(int i = 0; i < noThread; i++)
{
pthread_join(threadA[i], NULL);
}
cout << "All threads have joined" << endl;
}
void *task1 (void *dummyPt)
{
cout << "Thread No: " << pthread_self() << endl;
char test[300];
char outbuf[300];
bzero(outbuf, 301);
bzero(test, 301);
bool loop = false;
int recvdBytes = 0;
strcpy(outbuf, "Enter your username: \n");
write(connFd, outbuf, strlen(outbuf));
bzero(outbuf, 301);
read(connFd, test, 300);
string uname(test);
strcpy(outbuf, "You are logged in\n");
write(connFd, outbuf, strlen(outbuf));
bzero(outbuf, 301);
while(!loop)
{
bzero(test, 301);
read(connFd, test, 300);
string tester (test);
cout << tester << endl;
if(tester == "exit")
break;
for (int i=0; i<10; ++i)
{
strcpy(outbuf, "In response to your command");
write(connFd, outbuf, strlen(outbuf));
bzero(outbuf, 301);
}
}
cout << "\nClosing thread and conn" << endl;
close(connFd);
}
client.cpp
# include <string.h>
# include <cstring>
# include <unistd.h>
# include <stdio.h>
# include <netdb.h>
# include <sys/types.h>
# include <sys/socket.h>
# include <netinet/in.h>
# include <iostream>
# include <fstream>
# include <sstream>
# include <iomanip>
# include <strings.h>
# include <stdlib.h>
# include <string>
# include <time.h>
# include <vector>
using namespace std;
int main (int argc, char* argv[])
{
int sockFd, portNo;
bool loop = false;
struct sockaddr_in svrAdd;
struct hostent *server;
char inbuf[300];
int recvdBytes=0;
if(argc < 3)
{
cerr << "Syntax : ./client <host name> <port>"<<endl;
return 0;
}
portNo = atoi(argv[2]);
if((portNo > 65535) || (portNo < 2000))
{
cerr << "Please enter port number between 2000 - 65535"<<endl;
return 0;
}
//create client skt
sockFd = socket(AF_INET, SOCK_STREAM, 0);
if(sockFd < 0)
{
cerr << "Cannot open socket" << endl;
return 0;
}
server = gethostbyname(argv[1]);
if(server == NULL)
{
cerr << "Host does not exist" << endl;
return 0;
}
bzero((char *) &svrAdd, sizeof(svrAdd));
svrAdd.sin_family = AF_INET;
bcopy((char *) server -> h_addr, (char *) &svrAdd.sin_addr.s_addr, server -> h_length);
svrAdd.sin_port = htons(portNo);
int checker = connect(sockFd,(struct sockaddr *) &svrAdd, sizeof(svrAdd));
if (checker < 0)
{
cerr << "Cannot connect!" << endl;
return 0;
}
recvdBytes = read(sockFd, inbuf, 300);
cout << inbuf;
bzero(inbuf, 300);
cin >> inbuf;
write(sockFd, inbuf, strlen(inbuf)); // sending my user name to server
bzero(inbuf, 300);
read(sockFd, inbuf, 300); // recieving the message from server
cout << inbuf;
bzero(inbuf, 300);
// send commands to server
for(;;)
{
char s[300];
//cin.clear();
//cin.ignore(256, '\n');
cout << "Enter command: ";
bzero(s, 301);
cin.getline(s, 300);
write(sockFd, s, strlen(s));
// recieve data in response to your command
while(read(sockFd, inbuf, 300))
{
if(strcmp(inbuf, "done") == 0) // display the output
break;
cout << inbuf;
bzero(inbuf, 300);
}
}
}

Answer 1

Usual problems.
connFD should not be static. It should be a local variable in both main() and task1(), and it should be communicated to the started thread somehow. Otherwise the next client will clobber it and break the first client.
You aren't error-testing listen().
You're ignoring the result of read() everywhere. You have to store it into a variable and check it for -1, zero, or a positive value: only in the positive case should the loop continue; and the positive value should be used to limit the number of bytes in the buffer you regard as having been received.
You are ignoring the result of write() everywhere.
So at present there is no evidence that anything has been sent anywhere by anybody.