Network programming-simple UDP client/server mode

Non-connected communication is done through the UDP (User Datagram Protocol)/IP (Internet Protocol) protocol, which does not guarantee reliable data transfer, but can send data to multiple destinations or receive multiple source data. Compared to TCP and other connection communication, no connection communication as long as the service side first create sockets with socket (), and then through the bind () binding to specify the port, do not have to call listen (), accept (), only need to wait for the data.

UDP usage Scenarios: 1. The network data is mostly short message; 2. There is a large number of client;3. No special requirements for data security (after the message is sent, it is not possible to know if it is safe and complete); 4. The network burden is very heavy, but the response speed is high. Applications such as: C/S network application of network video conferencing system.

Client program Flow

Step1 initializing the socket library

Step2 Creating sockets

Socket sclient = socket (af_inet, SOCK_DGRAM, 0);

step3 Fill in the server address

sockaddr_in server;

memset (&server, 0, sizeof (sockaddr_in));

server.sin_family = af_inet;

SERVER.SIN_ADDR.S_ADDR = inet_addr (argv[1]);

Server.sin_port = htons ((u_short) atoi (argv[2]));

STEP4 Communication with the server (data communication) for information processing

(Send data)

Char buff[512] = {0};

strcpy (Buff, "I am Client");

int nret = sendto (sclient, Buff, strlen (buff) +1, 0, (struct sockaddr*) &server, sizeof (server));

(Receive data)

Char buff[512];

int naddrlen = sizeof (server);

memset (buff, 0, sizeof (buff));

Nret = Recvfrom (sclient, buff, sizeof (buff), 0, (struct sockaddr*) &server, &naddrlen);

STEP5 closing sockets after communication ends

STEP6 uninstalling the socket library

Server-Side Program flow

Step1 initializing the socket library

Step2 Creating sockets

Socket slisten= Socket (af_inet,sock_dgram,0)

step3 Create a local entity, fill in the native address information

Sockaddr_in Local;

memset (&local, 0, sizeof (local));

local.sin_family = af_inet;

LOCAL.SIN_ADDR.S_ADDR = Inaddr_any;

Local.sin_port = htons ((u_short) 8888);

STEP4 binding a fixed port

Bind (Slisten, (struct sockaddr *) &local, sizeof (local));

step5 receive client datagrams for processing and communication

Receive data

struct sockaddr_in from;

memset (&from, 0, sizeof (from));

int fromlen = sizeof (from);

Char buff[512] = {0};

Recvfrom (slisten,buff, sizeof (buff), 0, (struct sockaddr*) &from, &fromlen);

Send data

Char buff[512] = {0};

strcpy (Buff, "I am Server");

SendTo (Slisten, Buff, strlen (buff+1), 0, (struct sockaddr*) &from, Fromlen);

STEP6 closing sockets after communication ends

Closesocket (Slisten);

STEP7 uninstalling the socket library

　

　　

Network programming-simple UDP client/server mode