Problem sending multiple strings one by one using sockets

Question

I am new to socket programming. Need to send multiple strings one-by-one to server and collect the resulting string.

Now the problem is that using send/write function in client, all the strings are read in one go from server.

//client.c
sendString(serversocket,"str1"); 

sendString(serversocket,"str2"); 

sendString(serversocket,"str3"); 

//server.c

char *buff=readstring(clientsocket);

printf("%s",buff) ;//output : str1str2str2

Need to get str1, str2 and str3...

I need to make it as receive one after another. How can I do this? Any help would be appreciated.

Erik · Accepted Answer · 2011-03-11 10:05:00Z

3

A TCP socket is a byte stream - You will have to split up the data on the receiving end.

For strings, you can do this in e.g. one of these two ways:

Client:

send an integer length
send the string data

Server:

read an integer length
read this amount of bytes into a string

Or, you can use 0-termination:

Client:

send a string followed by a 0 byte

Server:

Read as much as possible, scan for 0 byte, extract string

You will have to handle both of these two cases on the server end:

Server receives 1 byte for each call to recv()
Server receives all data in a single call to recv()

answered Mar 11, 2011 at 10:05

Erik

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1 Comment

Sandeep Pathak Over a year ago

Thanks Erik.....I implemented this and this worked fine...Learned need to handle above two cases you mentioned ...

Nick · Accepted Answer · 2011-03-11 10:05:42Z

0

I assume you're using TCP here. In which case anything sent to the socket is treated as a stream. So you'll have to add separators into the stream in order to split the strings. You could send a newline after each string and then parse the input to split the lines again.

answered Mar 11, 2011 at 10:05

Nick

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Comments

Robert S. Barnes · Accepted Answer · 2011-03-11 10:15:33Z

0

Since TCP is a byte stream you need to delimit your pieces of data, i.e. your logical packets. In this case a newline character '\n' may be the most obvious choice, or you could use the null charater, '\0'.

//client.c
sendString(serversocket,"str1\n"); 

sendString(serversocket,"str2\n"); 

sendString(serversocket,"str3\n");

You could then use something like strtok to chop up the input data into it's component logical packets.

answered Mar 11, 2011 at 10:15

Robert S. Barnes

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