UDP----Socket Communication

Socket programming based on UDP (not connection-oriented), divided into client and server side.

The process for the client is as follows:

(1) Create socket (socket)

(2) Communication with the server (sendto)

(3) Close socket

SendTo function: to send data to a specified destination, sendto () for sending UDP packets with no established connection

ssize_t sendto (int sockfd, const void *buf, size_t len, int flags,

const struct SOCKADDR *dest_addr, socklen_t Addrlen);

The return value is integer and, if successful, returns the number of bytes sent, and the failure returns SOCKET_ERROR.

SOCKFD: Sockets

BUF: Buffer for data to be sent

Len: Buffer length

Flags: Call way flag bit, typically 0, change flags, will change the form of sendto send: Blocking

addr: (optional) Pointers , the address that points to the destination socket

Addr:lenaddr the length of the address referred to

The server-side process is as follows:

(1) Create socket (socket)

(2) Bind sockets to a local address and port (BIND)

(3) Communicating with the client using the returned socket (recvfrom)

(4) Return, wait for another customer to request.

(5) Close the socket.

recvfrom function: This function is used from (connected) Socket Interface and captures the address of the source that sent the data.

#include <sys/types.h>

#include <sys/socket.h>

ssize_t recvfrom (int sockfd, void *buf, size_t len, int flags,

struct sockaddr *src_addr, socklen_t *addrlen);

SOCKFD: Identifies a connected Socket Interface description of the word.

buf: Receive Data Buffers .

Len: buffers length.

Flags: Invoke operation mode.

src_addr: (optional) Pointers , pointing to the buffer that contains the source address. --Output type parameter

Addrlen: (optional) pointer, pointing to the from buffer length value. --Input and output type parameters.

The return value is integer and, if successful, returns the number of bytes received, and the failure returns SOCKET_ERROR.

Server-Side #include<stdio.h>                                                                           #include <stdlib.h> #include <errno.h> #include <string.h> #include <sys/ socket.h> #include <sys/types.h> #include <netinet/in.h> #include <arpa/inet.h>void usage ( Const char* proc) {    printf ("%s [ip][port]\n");} Int main (int argc,char* argv[]) {    if (argc!=3) {         usage (argv[0]);        return 1;     }    int sOck=socket (af_inet,sock_dgram,0);     if (sock<0) {         perror ("socket");        return 2;     }    int _port=atoi (argv[2]);    char* _ip=argv[1];     struct sockaddr_in local;    local.sin_family=AF_INET;     local.sin_port=htons (_port);     local.sin_addr.s_addr=inet_addr (_ IP);     if (Bind (sock, (struct sockaddr*) &local,sizeof (local) <0) {         perror ("bind");         exit (1);     }    char buf[1024];    struct  sockaddr_in remote;    socklen_t len=sizeof (remote);     while (1)     {&Nbsp;       ssize_t _s=recvfrom (sock,buf,sizeof (BUF) -1,0, (struct  sockaddr*) &remote,&len)         if (_s>0)     &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;{&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;BUF[_S] = ' + ';             printf ("client:[ip:%s][port:%d")   %s ", Inet_ntoa (REMOTE.SIN_ADDR), Ntohs (Remote.sin_port), buf);          }         else if (_s==0) {             printf ("Client close");             break;        }         else        {             break;        }     }    close (sock);     return 0;} Client Side #include<stdio.h>                                                                           #include <stdlib.h> #include <errno.h> #include <sys/socket.h> #include <sys/ types.h> #include <netinet/in.h> #include <arpa/inet.h> #include <string.h>void usage ( Const char* proc) {    printf ("%s[ip][port]", proc);} Int main (int argc,char* argv[]) {    if (argc!=3) {        usage (argv[0]);         return 1;    }    int sock=socket (AF_INET,SOCK_ dgram,0)     if (sock<0) {        perror ("socket") );        return 2;    }     int _port=atoi (argv[2]);    char* _ip=argv[1];     struct sockaddr_in client;    client.sin_family=af_inet;     Client.sin_port=htons (_port);     client.sin_addr.s_addr=inet_addr (_IP);     char buf[1024];    while (1)     {         ssize_t _s=read (0,buf,sizeof (BUF)-1);         if (_s>0) {             buf[_s]= ';         }        _s=sendto (sock,buf,sizeof (BUF) -1,0, (struct  sockaddr*) &client,sizeof (client));     }    return 0;}

Run:

650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M00/80/67/wKiom1dADyaBR6V6AAAzI-DUquY400.png "title=" 206. PNG "alt=" Wkiom1dadyabr6v6aaazi-duquy400.png "/>

This article is from the "Small Stop" blog, please be sure to keep this source http://10541556.blog.51cto.com/10531556/1775684

UDP----Socket Communication