linux C ----- udp, tcp, unix socket通信简单例子

linux C ----- udp, tcp, unix socket通信简单例子

udp socket

相关知识

UDP的程序设计可以分成客户端和服务器端两个部分。两者的主要差别在于对地址的绑定函数，客户端可以不用进行地质和端口的绑定。（客户端是随机拿一个大于1024的端口去连接的） 和TCP相比，UDP缺少connect(),listen(),accept()函数 【因为tcp面向连接，而UDP是无连接的。】 服务端的UDP编程：

客户端和服务端相比没有绑定bind()的步骤。

服务端的recvfrom是阻塞的，直到接收到数据。 关键词：数据包套接字，套接字文件描述符。

socket常见的套接字类型： - AF_INET（又称 PF_INET)是IPv4网络协议的套接字类型 - AF_INET6 是IPv6网络协议的套接字类型 - AF_UNIX 属于Unix系统本地通信

socket常见的套接字选项：

int s=socket(AF_INET,SOCK_DGRAM,0); if(s==-1){ perror("create socket: "); return -1; } struct sockaddr serv; serv.sin_family=AF_INET; serv.sin_addr.s_addr=htol(INADDR_ANY); // 任意本地IP，网络字节序 serv.sin_port=htos(PORT); //网络字节序 bind(s,(struct sockaddr*)&serv,sizeof(serv)); //绑定套接字和地址

解释“绑定套接字和地址”，实质上是指明发送数据的IP和端口。

关于sockaddr和sockaddr_in的区别：

它们的联系:

udp socket 例子

编写一个程序，使用udp通信，client是10.21.1.142, server是10.21.1.229，port是3000. client发送end能使得程序结束。 客户端：

#include #include #include #include #include #include #define PORT 3000int main(){ int s=socket(AF_INET,SOCK_DGRAM,0); if(s==-1){ perror("create socket error: "); exit(1); } struct sockaddr_in serv; bzero(&serv,sizeof(serv)); serv.sin_family=AF_INET; serv.sin_addr.s_addr = inet_addr("10.21.1.229"); //htonl(INADDR_ANY); serv.sin_port=htons(PORT); char buff[105]; int ret; while(1){ ret=read(STDIN_FILENO,buff,105); if(ret==-1){ perror("read error: "); break; } buff[ret]=0; sendto(s,buff,strlen(buff),0,(struct sockaddr *)&serv,sizeof(serv)); if(strcmp(buff,"end\n")==0){ printf("client process end.\n"); break; } int addr_len=sizeof(serv); if((ret=recvfrom(s,buff,105,0,(struct sockaddr *)&serv,&addr_len))==-1){ perror("recvform error: "); break; } buff[ret]=0; printf("receive message from server: %s",buff); } close(s); return 0;}

服务端：

#include #include #include #include #include #include #define PORT 3000int main(){ int s=socket(AF_INET,SOCK_DGRAM,0); if(s==-1){ perror("create socket error: "); exit(1); } struct sockaddr_in serv,client; bzero(&serv,sizeof(serv)); serv.sin_family=AF_INET; serv.sin_addr.s_addr=inet_addr("10.21.1.229");//htol(INADDR_ANY); serv.sin_port=htons(PORT); //网络字节序 if(bind(s,(struct sockaddr*)&serv,sizeof(serv))==-1){//绑定套接字和地址 perror("bind error: "); exit(1); } while(1){ char buff[105]; int addr_len=sizeof(client); int ret=recvfrom(s,buff,105,0,(struct sockaddr *)&client,&addr_len); // once success, we get client. if(ret==-1){ perror("recvfrom error: "); break; } buff[ret]=0; if(strcmp(buff,"end\n")==0){ printf("server process end.\n"); break; } printf("receive message from client: %s",buff); ret=read(STDIN_FILENO,buff,sizeof(buff)); if(ret<0){ perror("read error: "); break; } if(sendto(s,buff,ret,0,(struct sockaddr *)&client,addr_len)==-1){ perror("sendto error: "); break; } } close(s); return 0;}

会话:

$ ./udp1 hello, I'm clientreceive message from server: I'm server, I got message.oh, congratulation.receive message from server: hahahaendclient process end.$ ./udp1 receive message from client: hello, I'm clientI'm server, I got message.receive message from client: oh, congratulation.hahahaserver process end.

tcp socket

相关知识

通用的套接字地址

struct sockaddr{unsigned short int sa_family;char sa_data[14];};

用户和内核进行数据交互:

得到数据: recv(), accept()

传入数据: send(), bind()

表示地址长度的参数在得到数据的函数中是传地址的, 而在传入数据的函数则是传值的. (对比accept和bind就知道这是正确的.)

tcp server and client work as:

tcp socket 例子

编写tcp socket通信例子, 分为客户端和服务端部分,当客户端发送”end”时,结束程序. tcp_server.c:

#include #include #include #include #include #include #include const int port = 3000;const int MAX = 10; /* biggest number of connected clients */const char IP[] = "192.168.123.4";int main(){ int server_fd=socket(AF_INET,SOCK_STREAM,0); if(server_fd == -1){ perror("socket: "); return -1; } struct sockaddr_in server; bzero(&server,sizeof(server)); server.sin_family=AF_INET; server.sin_addr.s_addr=htonl(INADDR_ANY); //inet_addr(IP); /* both ways are ok. */ server.sin_port=htons(port); if(bind(server_fd,(struct sockaddr *)&server,sizeof(server))==-1){ perror("bind: "); return -1; } if(listen(server_fd,MAX) == -1){ perror("listen: "); return -1; } struct sockaddr_in client; int client_len=sizeof(client); int conn = accept(server_fd, (struct sockaddr *)&client, &client_len); if(conn == -1){ perror("accept: "); return -1; } char buff[105]; while(1){ memset(buff,0,sizeof(buff)); if(read(conn,buff,sizeof(buff)) == -1){ perror("read: "); break; } if(strcmp(buff,"end\n") == 0){ puts("the server process end. "); break; } printf("recv message from client: %s", buff); memset(buff,0,sizeof(buff)); if(read(STDIN_FILENO,buff,sizeof(buff)) == -1){ perror("read: "); break; } if(write(conn,buff,strlen(buff)) == -1){ perror("send: "); break; } } close(conn); close(server_fd); return 0;}

tcp_client.c:

#include #include #include #include #include #include #include const int port = 3000;const int MAX = 10; /* biggest number of client_fdected clients */const char IP[] = "192.168.123.4";int main(){ int client_fd=socket(AF_INET,SOCK_STREAM,0); if(client_fd == -1){ perror("socket: "); return -1; } struct sockaddr_in server; bzero(&server,sizeof(server)); server.sin_family=AF_INET; server.sin_addr.s_addr=inet_addr(IP); server.sin_port=htons(port); if(connect(client_fd,(struct sockaddr *)&server,sizeof(server))==-1){ perror("client_fdect: "); return -1; } char sends[105],recvs[105]; while(1){ read(STDIN_FILENO,sends,sizeof(sends)); if(send(client_fd,sends,strlen(sends),0)==-1){ perror("send: "); break; } if(strcmp(sends,"end\n") == 0){ puts("the client end."); break; } memset(recvs,0,sizeof(recvs)); if(read(client_fd,recvs,sizeof(recvs))==-1){ perror("recv: "); break; } printf("recv message from server: %s",recvs); memset(sends,0,sizeof(sends)); } close(client_fd); return 0;}

会话:

./tcpsrecv message from client: helloI got your message.recv message from client: ok, every thins seems good.client, we works.the server process end../tcpchellorecv message from server: I got your message.ok, every thins seems good.recv message from server: client, we works.endthe client end.

Unix socket

相关知识

Unix域协议族用于同一台主机上客户机、服务器通信。 Unix域中两种类型的套接字：字节流套接字（类似于tcp）、数据包套接字（类似于udp）。 Unix域套接字的传输速度是tcp的两倍。 Unix域套接字和传统套接字相比，他是用路径名来表示协议族的描述。 Unix域地质结构：

#definestruct sockaddr_un { __kernel_sa_family_t sun_family; /* AF_UNIX */ char sun_path[UNIX_PATH_MAX]; /* pathname */

sun_family: AF_UNIX (known as AF_LOCAL) sun_path: 必须是绝对路径，文件默认访问权限是0777

unix socket例子

一个客户端和服务器通信(本地)的例子. 当客户端发送end时,结束会话. un_sock_serv.c:

#include #include #include #include #include const char path[]="/tmp/server";int main(){ int server_fd,client_fd; struct sockaddr_un server_addr, client_addr; unlink(path); server_fd = socket(AF_UNIX,SOCK_STREAM,0); if(server_fd == -1){ perror("socket: "); exit(1); } server_addr.sun_family=AF_UNIX; strcpy(server_addr.sun_path,path); if(bind(server_fd,(struct sockaddr *)&server_addr,sizeof(server_addr))==-1){ perror("bind: "); exit(1); } listen(server_fd,10); //server listen most 10 requests. puts("server is listening: "); int client_len=sizeof(client_addr); client_fd=accept(server_fd,(struct sockaddr *)&client_addr,(int *)&client_len); if(client_fd == -1){ perror("accept: "); exit(1); } char recv[105], send[105]; int i; while(1){ memset(recv,0,sizeof(recv)); if(read(client_fd,recv,105)==-1){ perror("read: "); break; } if(strcmp(recv,"end\n")==0){ printf("the server process end.\n"); break; } printf("recv message from client: %s",recv); memset(send,0,sizeof(send)); if(read(STDIN_FILENO,send,sizeof(send))==-1){ perror("read: "); break; } if(write(client_fd,send,strlen(send))==-1){ perror("write: "); break; } } close(server_fd); unlink(path);}

un_sock_client.c:

#include #include #include #include #include const char path[]="/tmp/server";int main(){ int server_fd,client_fd; struct sockaddr_un server_addr, client_addr; //unlink(path); server_fd = socket(AF_UNIX,SOCK_STREAM,0); if(server_fd == -1){ perror("socket: "); exit(1); } server_addr.sun_family=AF_UNIX; strcpy(server_addr.sun_path,path); if(connect(server_fd,(struct sockaddr *)&server_addr,sizeof(server_addr)) == -1){ perror("connect: "); exit(1); } char recv[105],send[105]; int i; puts("the client started, please enter your message: "); while(1){ memset(send,0,sizeof(send)); if(read(STDIN_FILENO,send,105)==-1){ perror("read: "); break; } if(write(server_fd,send,strlen(send))==-1){ perror("send: "); break; } if(strcmp(send,"end\n")==0){ printf("the client process end.\n"); break; } memset(recv,0,sizeof(recv)); if(read(server_fd,recv,105)==-1){ perror("recv: "); break; } printf("recv message from server: %s",recv); } close(server_fd); unlink(path); return 0;}

会话:

$ ./exesserver is listening: recv message from client: hello, I'm clientI'm server, I get your message.recv message from client: ok, it seems goods.yeah, it works.the server process is end.$ ./execthe client started, please enter your message: hello, I'm clientrecv message from server: I'm server, I get your message.ok, it seems goods.recv message from server: yeah, it works.endthe client process end.

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