maximum data that can be sent through a port-socket - c

Question

i have implemented a program which takes input from client, performs operation on server and writes the data to the client. ls command is what i have chosen for example.
Now my doubt is,
1) what if the input is very huge in bytes??
2) what is the maximum data that can be sent through a socket port??
client.c
int main()
{
FILE *fp;
int servfd, clifd;
struct sockaddr_in servaddr;
struct sockaddr_in cliaddr;
int cliaddr_len;
char str[4096], clientip[16];
int n;
servfd = socket(AF_INET, SOCK_STREAM, 0);
if(servfd < 0)
{
perror("socket");
exit(5);
}
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERVPORT);
servaddr.sin_addr.s_addr = inet_addr(SERVIP);
if(bind(servfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0)
{
perror("bind");
exit(0);
}
listen(servfd, 5);
printf("Server is waiting for client connection.....\n");
while(1)
{
cliaddr_len=sizeof(cliaddr);
clifd = accept(servfd, (struct sockaddr *)&cliaddr, &cliaddr_len);
strcpy(clientip, inet_ntoa(cliaddr.sin_addr));
printf("Client connected: %s\n", clientip);
if(fork() == 0)
{
close(servfd);
while(1)
{
n = read(clifd, str, sizeof(str));
str[n] = 0;
if(strcmp(str, "end") == 0)
{
printf("\nclient(%s) is ending session and server is waiting for new connections\n\n", clientip);
break;
}
else if (strcmp(str, "ls") == 0) {
system("ls >> temp.txt");
fp = fopen("temp.txt", "r");
fread(str, 1, 500, fp);
remove("temp.txt");
}
else
printf("Received from client(%s): %s\n", clientip, str);
write(clifd, str, strlen(str));
}
close(clifd);
exit(0);
}
else
{
close(clifd);
}
}
}
server.c
int main()
{
int sockfd;
struct sockaddr_in servaddr;
char str[500];
int n;
sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERVPORT);
servaddr.sin_addr.s_addr = inet_addr(SERVIP);
if(connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0)
{
printf("Could not connect to server: %s\n", strerror(errno));
exit(1);
}
while(1)
{
printf("Enter message: ");
scanf(" %[^\n]", str);
write(sockfd, str, strlen(str));
if(strcmp(str, "end") == 0)
break;
n = read(sockfd, str, sizeof(str));
str[n] = 0;
printf("Read from server: %s\n", str);
}
close(sockfd);
}

Answer 1

As for your question no 1. the huge data is broken in many packets & then sent packet by packet its done by OS internally. & the one packet size depends on your system OS(you can change it.It is called MTU maximum transfer unit).
& for your question no 2. the data send by a socket port may be infinite coz as long as u wish to send data it will send. there is no limit.!!!

Answer 2

Q: What if the input is very huge in bytes?? What is the maximum data that can be sent through a socket port??
A: There is no limit on the size of a TCP/IP stream. In theory, you could send and receive an infinite number of bytes.
... HOWEVER ...
1) The receiver must never assume is will ever get all the bytes at once, in a single read. You must always read socket data in a loop, reading as much at a time as you wish, and appending it to the data you've already read.
2) You can send a "large" amount of data at once, but the OS will buffer it behind your back.
3) Even then, there's an OS limit. For example, here the maximum send buffer size is 1 048 576 bytes.:
http://publib.boulder.ibm.com/infocenter/tpfhelp/current/index.jsp?topic=%2Fcom.ibm.ztpf-ztpfdf.doc_put.cur%2Fgtpc2%2Fcpp_send.html
If you need to send more, you must send() in a loop.
PS:
As Anish recommended, definitely check out Beej's Guide to Network programming:
http://beej.us/guide/bgnet/output/html/multipage/