C++ || Snippet – How To Send Text Over A Network Using A UDP Connection

January 08, 2014 admin No comments

The following is sample code which demonstrates the use of the “socket“, “bind“, “recvfrom“, and “sendto” function calls for interprocess communication over a network on Unix based systems.

The following example demonstrates a simple network application in which a client sends text to a server, and the server replies (sends text) back to the client. This program demonstrates communication between two programs using a UDP connection.

Click here to examine the TCP version.

Note: The server program must be ran before the client program!

=== 1. SERVER ===





		
		
			IPC Networking - UDP Server
			
C++
			
			// ============================================================================
//   Author: K Perkins
//   Date:  Jan 8, 2014
//   Taken From: http://programmingnotes.org/
//   File: ServerUDP.cpp
//   Description: This program implements a simple network application in 
//     which a client sends text to a server and the server replies back to the
//     client. This is the server program, and has the following functionality:
//       1. Listen for incoming connections on a specified port.
//       2. When a client connects, text is received from the client.
//       3. Text is sent back to the client from the server.
//       4. Go back to waiting for more connections.
// ============================================================================
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <sys/socket.h>
#include <netinet/in.h>
using namespace std;

// Compile & Run
// g++ ServerUDP.cpp -o ServerUDP
// ./ServerUDP 1234

// the maximum size for sending/receiving text
const int MSG_SIZE = 100;

int main(int argc, char* argv[])
{
    // declare variables
    // to store the port number
    int port = -1;

    // to store the socket file descriptor
    int socketfd = -1;

    // the address structures for the server and the client
    sockaddr_in servaddr, cliaddr;

    // the size of sockaddr_in structure
    socklen_t sockaddr_in_len = 0;

    // the number of bytes received and sent
    int numRead = -1, numSent = -1;	
		
    // the buffer to store the string to send/receive
    char data[MSG_SIZE];

    // check the command line
    if(argc < 2)
    {
	    cerr<<"n** ERROR NOT ENOUGH ARGS!n"
	        <<"USAGE: "<<argv[0]<<" <SERVER PORT #>n";
	    exit(1);
    }
	
    // convert the port number to an integer
    port = atoi(argv[1]);

    // make sure the port range is valid
    if(port < 0 || port > 65535)	
    {
	    cerr<<"nInvalid port numbern";
	    exit(1);
    } 	
	
    // create a UDP socket
    if((socketfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
	    perror("socket");
	    exit(1);
    }	
	
    // clear the structure for the server address
    memset(&servaddr, 0, sizeof(servaddr));

    // populate the server address structure
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(port);

    // bind the socket to the port
    if(bind(socketfd,(sockaddr *)&servaddr, sizeof(servaddr)) < 0)
    {
	    perror("bind");
	    exit(1);
    }

    cerr<<"nServer started!n";
    
    // keep receiving forever
    while(true)
    {
        cerr<<"nWaiting for someone to connect..n";
            
        // get the size of the client address data structure
        sockaddr_in_len = sizeof(cliaddr);	

        // get something from the client; Will block until the client sends. 
        if((numRead = recvfrom(socketfd, data, sizeof(data), 0, 
            (sockaddr *)&cliaddr, &sockaddr_in_len)) < 0)
        {
            perror("recvfrom");
            exit(1);
        }	

        cerr<<"nRECEIVED: ""<<data<<"" from the clientn";
        //cerr<<"Bytes read: "<<numRead<<endl;          

        // set the array to all zeros 
        memset(&data, 0, sizeof(data));	

        // retrieve the time 
        time_t rawtime;
        time(&rawtime);
        struct tm* timeinfo;
        timeinfo = localtime(&rawtime);                	    	    
        strftime(data, sizeof(data),"%a, %b %d %Y, %I:%M:%S %p", timeinfo);
                
        cerr<<"nSENDING: ""<<data<<"" to the clientn";	

        // send the time to the client
        if((numSent = sendto(socketfd, data, strlen(data)+1, 0,
            (sockaddr *)&cliaddr,sizeof(cliaddr))) < 0)
        {
            perror("sendto");
            exit(1);
        }
    }

    return 0;
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
				
						// ============================================================================
//   Author: K Perkins
//   Date:  Jan 8, 2014
//   Taken From: http://programmingnotes.org/
//   File: ServerUDP.cpp
//   Description: This program implements a simple network application in 
//     which a client sends text to a server and the server replies back to the
//     client. This is the server program, and has the following functionality:
//       1. Listen for incoming connections on a specified port.
//       2. When a client connects, text is received from the client.
//       3. Text is sent back to the client from the server.
//       4. Go back to waiting for more connections.
// ============================================================================
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <sys/socket.h>
#include <netinet/in.h>
using namespace std;
 
// Compile & Run
// g++ ServerUDP.cpp -o ServerUDP
// ./ServerUDP 1234
 
// the maximum size for sending/receiving text
const int MSG_SIZE = 100;
 
int main(int argc, char* argv[])
{
    // declare variables
    // to store the port number
    int port = -1;
 
    // to store the socket file descriptor
    int socketfd = -1;
 
    // the address structures for the server and the client
    sockaddr_in servaddr, cliaddr;
 
    // the size of sockaddr_in structure
    socklen_t sockaddr_in_len = 0;
 
    // the number of bytes received and sent
    int numRead = -1, numSent = -1;	
		
    // the buffer to store the string to send/receive
    char data[MSG_SIZE];
 
    // check the command line
    if(argc < 2)
    {
	    cerr<<"n** ERROR NOT ENOUGH ARGS!n"
	        <<"USAGE: "<<argv[0]<<" <SERVER PORT #>n";
	    exit(1);
    }
	
    // convert the port number to an integer
    port = atoi(argv[1]);
 
    // make sure the port range is valid
    if(port < 0 || port > 65535)	
    {
	    cerr<<"nInvalid port numbern";
	    exit(1);
    } 	
	
    // create a UDP socket
    if((socketfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
	    perror("socket");
	    exit(1);
    }	
	
    // clear the structure for the server address
    memset(&servaddr, 0, sizeof(servaddr));
 
    // populate the server address structure
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(port);
 
    // bind the socket to the port
    if(bind(socketfd,(sockaddr *)&servaddr, sizeof(servaddr)) < 0)
    {
	    perror("bind");
	    exit(1);
    }
 
    cerr<<"nServer started!n";
    
    // keep receiving forever
    while(true)
    {
        cerr<<"nWaiting for someone to connect..n";
            
        // get the size of the client address data structure
        sockaddr_in_len = sizeof(cliaddr);	
 
        // get something from the client; Will block until the client sends. 
        if((numRead = recvfrom(socketfd, data, sizeof(data), 0, 
            (sockaddr *)&cliaddr, &sockaddr_in_len)) < 0)
        {
            perror("recvfrom");
            exit(1);
        }	
 
        cerr<<"nRECEIVED: ""<<data<<"" from the clientn";
        //cerr<<"Bytes read: "<<numRead<<endl;          
 
        // set the array to all zeros 
        memset(&data, 0, sizeof(data));	
 
        // retrieve the time 
        time_t rawtime;
        time(&rawtime);
        struct tm* timeinfo;
        timeinfo = localtime(&rawtime);                	    	    
        strftime(data, sizeof(data),"%a, %b %d %Y, %I:%M:%S %p", timeinfo);
                
        cerr<<"nSENDING: ""<<data<<"" to the clientn";	
 
        // send the time to the client
        if((numSent = sendto(socketfd, data, strlen(data)+1, 0,
            (sockaddr *)&cliaddr,sizeof(cliaddr))) < 0)
        {
            perror("sendto");
            exit(1);
        }
    }
 
    return 0;
}// http://programmingnotes.org/

=== 2. CLIENT ===





		
		
			IPC Networking - UDP Client
			
C++
			
			// ============================================================================
//   Author:  K Perkins
//   Date:  Jan 8, 2014
//   Taken From: http://programmingnotes.org/
//   File: ClientUDP.cpp
//   Description: This program implements a simple network application in 
//     which a client sends text to a server and the server replies back to the
//     client. This is the client program, and has the following functionality:
//       1. Send text to the server on a specified port.
//       2. Recieve text from the server and exit.
// ============================================================================
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
using namespace std;

// Compile & Run
// g++ ClientUDP.cpp -o ClientUDP
// ./ClientUDP 127.0.0.1 1234

// the maximum size for sending/receiving text
const int MSG_SIZE = 100;

int main(int argc, char* argv[])
{
    // declare variables
    // to store the port number
    int port = -1;

    // to store the socket file descriptor
    int socketfd = -1;

    // the address structures for the server and the client
    sockaddr_in servaddr, cliaddr;

    // the size of sockaddr_in structure
    socklen_t sockaddr_in_len = 0;

    // the number of bytes received and sent
    int numRead = -1, numSent = -1;	
		
    // the buffer to store the string to send/receive
    char data[MSG_SIZE] = "Server, what time is it?";

    // check the command line
    if(argc < 3)
    {
	    cerr<<"n** ERROR NOT ENOUGH ARGS!n"
	        <<"USAGE: "<<argv[0]<<" <SERVER IP> <SERVER PORT #>n";
	    exit(1);
    }
	
    // convert the port number to an integer
    port = atoi(argv[2]);

    // make sure the port range is valid
    if(port < 0 || port > 65535)	
    {
	    cerr<<"nInvalid port numbern";
	    exit(1);
    } 	
	
    // create a UDP socket
    if((socketfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
	    perror("socket");
	    exit(1);
    }

    // clear the structure for the server address
    memset(&servaddr, 0, sizeof(servaddr));

    // populate the server address structure
    servaddr.sin_family = AF_INET;
	
    // initialize the IP address of the server
    if(!inet_pton(AF_INET, argv[1], &servaddr.sin_addr.s_addr))
    {
	    perror("inet_pton");
	    exit(1);
    }

    // set the port
    servaddr.sin_port = htons(port);

    // get the size of the client address data structure
    sockaddr_in_len = sizeof(cliaddr);
    
    cerr<<"nSENDING: ""<<data<<"" to the servern";

    // send the time to the client
    if((numSent = sendto(socketfd, data, strlen(data)+1, 0,
				    (sockaddr *)&servaddr, sizeof(servaddr))) < 0)
    {
	    perror("sendto");
	    exit(1);
    }

    // get something from the client; Will block until the client sends. 
    if((numRead = recvfrom(socketfd, data, sizeof(data), 0, 
				    (sockaddr *)&cliaddr, &sockaddr_in_len)) < 0)
    {
	    perror("recvfrom");
	    exit(1);
    }

    // NULL terminate the received string 
    data[numRead] = '�';
	
    cerr<<"nRECEIVED: ""<<data<<"" from the servern"; 
    //cerr<<"Bytes read: "<<numRead<<endl;

    return 0;
}// http://programmingnotes.org/
			
				
					
				
					1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
				
						// ============================================================================
//   Author:  K Perkins
//   Date:  Jan 8, 2014
//   Taken From: http://programmingnotes.org/
//   File: ClientUDP.cpp
//   Description: This program implements a simple network application in 
//     which a client sends text to a server and the server replies back to the
//     client. This is the client program, and has the following functionality:
//       1. Send text to the server on a specified port.
//       2. Recieve text from the server and exit.
// ============================================================================
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
using namespace std;
 
// Compile & Run
// g++ ClientUDP.cpp -o ClientUDP
// ./ClientUDP 127.0.0.1 1234
 
// the maximum size for sending/receiving text
const int MSG_SIZE = 100;
 
int main(int argc, char* argv[])
{
    // declare variables
    // to store the port number
    int port = -1;
 
    // to store the socket file descriptor
    int socketfd = -1;
 
    // the address structures for the server and the client
    sockaddr_in servaddr, cliaddr;
 
    // the size of sockaddr_in structure
    socklen_t sockaddr_in_len = 0;
 
    // the number of bytes received and sent
    int numRead = -1, numSent = -1;	
		
    // the buffer to store the string to send/receive
    char data[MSG_SIZE] = "Server, what time is it?";
 
    // check the command line
    if(argc < 3)
    {
	    cerr<<"n** ERROR NOT ENOUGH ARGS!n"
	        <<"USAGE: "<<argv[0]<<" <SERVER IP> <SERVER PORT #>n";
	    exit(1);
    }
	
    // convert the port number to an integer
    port = atoi(argv[2]);
 
    // make sure the port range is valid
    if(port < 0 || port > 65535)	
    {
	    cerr<<"nInvalid port numbern";
	    exit(1);
    } 	
	
    // create a UDP socket
    if((socketfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
	    perror("socket");
	    exit(1);
    }
 
    // clear the structure for the server address
    memset(&servaddr, 0, sizeof(servaddr));
 
    // populate the server address structure
    servaddr.sin_family = AF_INET;
	
    // initialize the IP address of the server
    if(!inet_pton(AF_INET, argv[1], &servaddr.sin_addr.s_addr))
    {
	    perror("inet_pton");
	    exit(1);
    }
 
    // set the port
    servaddr.sin_port = htons(port);
 
    // get the size of the client address data structure
    sockaddr_in_len = sizeof(cliaddr);
    
    cerr<<"nSENDING: ""<<data<<"" to the servern";
 
    // send the time to the client
    if((numSent = sendto(socketfd, data, strlen(data)+1, 0,
				    (sockaddr *)&servaddr, sizeof(servaddr))) < 0)
    {
	    perror("sendto");
	    exit(1);
    }
 
    // get something from the client; Will block until the client sends. 
    if((numRead = recvfrom(socketfd, data, sizeof(data), 0, 
				    (sockaddr *)&cliaddr, &sockaddr_in_len)) < 0)
    {
	    perror("recvfrom");
	    exit(1);
    }
 
    // NULL terminate the received string 
    data[numRead] = '';
	
    cerr<<"nRECEIVED: ""<<data<<"" from the servern"; 
    //cerr<<"Bytes read: "<<numRead<<endl;
 
    return 0;
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

The following is sample output.

SERVER OUTPUT:

Server started!
Waiting for someone to connect.. RECEIVED: "Server, what time is it?" from the client
SENDING: "Wed, Jan 08 2014, 11:47:12 PM" to the client

CLIENT OUTPUT:

SENDING: "Server, what time is it?" to the server
RECEIVED: "Wed, Jan 08 2014, 11:47:12 PM" from the server

Was this article helpful?

👍 YesNo

Posted in: Advanced, C++, C++, Snippets, Unix/Linux Tags: bind, cpsc 471, ipc, networking, read, recv, recvfrom, sendto, socket, udp

C++ || Snippet – How To Send Text Over A Network Using A UDP Connection

Related

Leave a ReplyCancel reply

Search

Compile Your Code Now

Translate Page

Popular Pages

Recent

Archives

Categories