Sending and Receiving Data

After the connect and accept calls are successfully executed, the connection is established and data can be sent and received between the two socket endpoints. Because the stream socket descriptors correspond to HP-UX file descriptors, you can use the read and write calls (in addition to recv and send) to pass data through a socket-terminated channel.

If you are considering the use of the read and write system calls instead of the send and recv calls described below, you should consider the following:

If you use read and write instead of send and recv, you can use a socket for stdin or stdout.
If you use read and write instead of send and recv, you cannot use the options specified with the send or recv flags parameter.

See the table that lists other system calls in chapter 8, for more information on which of these system calls are best for your application.

Sending Data

send and its parameters are described in the following table.

Include files:

#include <sys/types.h> 
#include <sys/socket.h>

System call:

count = send(s,msg,len,flags) 
int s; 
char *msg; 
int len, flags;

Parameter	Description of Contents	INPUT Value
s	socket descriptor of local socket	socket descriptor of socket sending data
msg	pointer to data buffer	pointer to data to be sent
len	size of data buffer	size of msg
flags	settings for optional flags	0 or MSG_OOB

Function result:

number of bytes actually sent, -1 if failure occurs.

Example:

count = send (s, buf, 10, 0);

send blocks until the specified number of bytes have been queued to be sent, unless you are using nonblocking I/O.

When to Send Data

The server or client process should send data after the connection is established. Refer to the send(2) man page for more information on send.

Receiving Data

recv and its parameters are described in the following table.

Include files:

#include <sys/types.h> 
#include <sys/socket.h>

System call:

count = recv(s,buf,len,flags) 
int s; 
char *buf; 
int len, flags;

Parameter	Description of Contents	INPUT Value
s	socket descriptor of local socket	socket descriptor of socket receiving data
buf	pointer to data buffer	pointer to buffer that is to receive data
len	maximum number of bytes that should be received	size of data buffer
flags	settings for optional flags	0, MSG_OOB or MSG_PEEK

Function result:

number of bytes actually received, -1 if failure occurs.

Example:

count = recv(s, buf, 10, 0);

recv blocks until there is at least 1 byte of data to be received, unless you are using nonblocking I/O. The host does not wait for len bytes to be available; if less than len bytes are available, that number of bytes are received.

No more than len bytes of data are received. If there are more than len bytes of data on the socket, the remaining bytes are received on the next recv.

Flag Options

The flag options are:

0 for no options.
MSG_OOB for out of band data.
MSG_PEEK for a nondestructive read .

Use the MSG_OOB option if you want to receive out of band data. Refer to the "Sending and Receiving Out of Band Data" section of chapter 3, "Advanced Topics for Stream Sockets," for more information.

Use the MSG_PEEK option to preview incoming data. If this option is set on a recv, any data returned remains in the socket buffer as though it had not been read yet. The next recv returns the same data.

When to Receive Data

The server or client process should receive data after connection is established. Refer to the recv(2) man page for more information on recv.

Sending and Receiving Data

Technical documentation

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Sending Data

When to Send Data

Receiving Data

Flag Options

When to Receive Data