Socket code problems

When I run this program, everything works as expected. It starts up and connects to a server and gets all the stuff the server is supposed to send. However, when I try to type something, it works, but then it won't listen to any more input and I don't think it recieves any more. I have no idea why.

Code:

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#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
 
#define SOCKET_ERROR        -1
#define BUFFER_SIZE        100
#define HOST_NAME_SIZE      255
 
int  main(int argc, char* argv[])
{
    int hSocket;                /* handle to socket */
    struct hostent* pHostInfo;  /* holds info about a machine */
    struct sockaddr_in Address;  /* Internet socket address stuct */
    long nHostAddress;
    char pBuffer[BUFFER_SIZE];
    unsigned nReadAmount;
    char strHostName[HOST_NAME_SIZE];
    int nHostPort;
    char buf[1024];
    int n;
 
    if(argc < 3)
      {
        printf("\nUsage: client host-name host-port\n");
        return 0;
      }
    else
      {
        strcpy(strHostName,argv[1]);
        nHostPort=atoi(argv[2]);
      }
 
    /* make a socket */
    hSocket=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
 
    if(hSocket == SOCKET_ERROR)
    {
        printf("\nCould not make a socket\n");
        return 0;
    }
 
    /* get IP address from name */
    pHostInfo=gethostbyname(strHostName);
    /* copy address into long */
    memcpy(&nHostAddress,pHostInfo->h_addr,pHostInfo->h_length);
 
    /* fill address struct */
    Address.sin_addr.s_addr=nHostAddress;
    Address.sin_port=htons(nHostPort);
    Address.sin_family=AF_INET;
printf("Connecting to %s on port %d\n",strHostName,nHostPort);
 
    /* connect to host */
    if(connect(hSocket,(struct sockaddr*)&Address,sizeof(Address))
      == SOCKET_ERROR)
    {
        printf("\nCould not connect to host\n");
        return 0;
    }
 
    /* read from socket into buffer
    ** number returned by read() and write() is the number of bytes
    ** read or written, with -1 being that an error occured */
    printf("Type a ~ to exit\n");
    printf("Enter to continue\n");
while(1)
    {
        gets(buf);
        if(buf[0] == '~')
            break;
        n = strlen(buf);
        buf[n] = '\n';
        buf[n+1] = 0;
        write(hSocket,buf, strlen(buf));
        nReadAmount = 1;
        while(nReadAmount > 0)
        {
            nReadAmount=read(hSocket,pBuffer,BUFFER_SIZE);
            pBuffer[nReadAmount] = '\0';
            printf("%s", pBuffer);
        }
        printf("\n>");
    }
    /* write what we received back to the server */
 
    printf("\nClosing socket\n");
    /* close socket */                     
    if(close(hSocket) == SOCKET_ERROR)
    {
        printf("\nCould not close socket\n");
        return 0;
    }
}

---

Wouldn't it be more appropriate to post this in the Networking/Device Communication or the Linux Programming forums?

Didn't anyone tell you to never ever use gets()?

Quote:

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Originally Posted by cwr

Wouldn't it be more appropriate to post this in the Networking/Device Communication or the Linux Programming forums?

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Yes, I accidently posted this is C. My mistake.

Quote:

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Originally Posted by ^xor

Didn't anyone tell you to never ever use gets()?

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Is get(); the thing that messes up my code?

moved

Quote:

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Originally Posted by Phan

Is get(); the thing that messes up my code?

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It's gets() and not get(), and I haven't looked closely at your code so I don't know if that's what causing it to break. But the mere presence of it in your code means that your program has a vulnerability, so use fgets or something similar.

> I have no idea why.
Well
nReadAmount=read(hSocket,pBuffer,BUFFER_SIZE);
has no idea how long to wait before deciding there is no more data to be read - it returns 0 when the socket closes.

So you need to make the read() non-blocking somehow (depends on your OS). But in Linux, I would use select() with a timeout to determine whether was anything interesting to be read.

Does read return anything if there is nothing more to read? Because I've currently been trying something like this:

Code:

---

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
 
#define SOCKET_ERROR        -1
#define BUFFER_SIZE        100
#define HOST_NAME_SIZE      255
 
int  main(int argc, char* argv[])
{
    int hSocket;                /* handle to socket */
    struct hostent* pHostInfo;  /* holds info about a machine */
    struct sockaddr_in Address;  /* Internet socket address stuct */
    long nHostAddress;
    char pBuffer[BUFFER_SIZE];
    unsigned nReadAmount;
    char strHostName[HOST_NAME_SIZE];
    int nHostPort;
    char buf[1024];
    int n;
 
    if(argc < 3)
      {
        printf("\nUsage: client host-name host-port\n");
        return 0;
      }
    else
      {
        strcpy(strHostName,argv[1]);
        nHostPort=atoi(argv[2]);
      }
 
    /* make a socket */
    hSocket=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
 
    if(hSocket == SOCKET_ERROR)
    {
        printf("\nCould not make a socket\n");
        return 0;
    }
 
    /* get IP address from name */
    pHostInfo=gethostbyname(strHostName);
    /* copy address into long */
    memcpy(&nHostAddress,pHostInfo->h_addr,pHostInfo->h_length);
 
    /* fill address struct */
    Address.sin_addr.s_addr=nHostAddress;
    Address.sin_port=htons(nHostPort);
    Address.sin_family=AF_INET;
printf("Connecting to %s on port %d\n",strHostName,nHostPort);
 
    /* connect to host */
    if(connect(hSocket,(struct sockaddr*)&Address,sizeof(Address))
      == SOCKET_ERROR)
    {
        printf("\nCould not connect to host\n");
        return 0;
    }
 
    /* read from socket into buffer
    ** number returned by read() and write() is the number of bytes
    ** read or written, with -1 being that an error occured */
    printf("Type a ~ to exit\n");
  nReadAmount=1;
 while(nReadAmount > 0)
        {
            nReadAmount=recv(hSocket,pBuffer,BUFFER_SIZE,0);
            pBuffer[nReadAmount] = '\0';
            if (pBuffer[nReadAmount]='\0') {
            nReadAmount = 0;
            break;
           
            } else
            {
           
            printf("%s", pBuffer);
        }
        }


while(nReadAmount = 0)
    {
        printf("\n>");
        gets(buf);
        if(buf[0] == '~')
            break;
        n = strlen(buf);
        buf[n] = '\n';
        buf[n+1] = 0;
        send(hSocket,buf, strlen(buf),0);
        nReadAmount = 1;
        break;
    }
    /* write what we received back to the server */

    printf("\nClosing socket\n");
    /* close socket */                     
    if(close(hSocket) == SOCKET_ERROR)
    {
        printf("\nCould not close socket\n");
        return 0;
    }
}

---

There isn't any thing wrong with it that I can see, excpet for the fact that I think I'm not getting the:
if (pBuffer[nReadAmount]='\0') {
nReadAmount = 0;
part right. Ideas?

Well
> if (pBuffer[nReadAmount]='\0')
> while(nReadAmount = 0)
are assignments, not comparisons, so who knows what's going on.

AFAIK, read() only returns 0 when the socket closes, not when there's nothing to read.

That is, unless you've made the socket non-blocking.

Ok, so I should probably use select then with a timeout. How would select() be used in a situation like this? select(blah, &readfds, NULL,NULL,&timeout); ?

http://faq.cprogramming.com/cgi-bin/...=1045780608#03

and also:
http://faq.cprogramming.com/cgi-bin/...&id=1044780608