Linux tcp客户端断开重连,Linux网络编程——TCP和UDP通信
TCP协议流程图、TCP建立即时聊天
TCP即时聊天升级：服务器在客户端断开后不断开，客户端可以多次重连服务器进行即时聊天
UDP协议流程图、UDP建立即时连接
如果在已经处于 ESTABLISHED状态下的socket(一般由端口号和标志符区分)需调用closesocket(一般不会立即关闭而经历TIME_WAIT的过程)后想继续重用该socket，但也可以直接用setsockopt和reuse。
SO_RCVLOWAT设置接收缓冲区下限
1、TCP协议的流程图
服务端：socket---bind---listen---while(1){---accept---recv---send---close---}---close
客户端：socket----------------------------------connect---send---recv-----------------close
TCP建立即时聊天
tcp_client.c
#include
int main(int argc,char* argv[])
{
ARGS_CHECK(argc,3);
int socketFd;
socketFd=socket(AF_INET,SOCK_STREAM,0);
ERROR_CHECK(socketFd,-1,"socket");
struct sockaddr_in ser;
bzero(&ser,sizeof(ser));
ser.sin_family=AF_INET;
ser.sin_port=htons(atoi(argv[2]));
ser.sin_addr.s_addr=inet_addr(argv[1]);//点分十进制转为32位的网络字节序
int ret;
ret=connect(socketFd,(struct sockaddr*)&ser,sizeof(ser));
ERROR_CHECK(ret, -1, "connect");
printf("connect success\n");
char buf[128]={0};
fd_set rdset;
while(1){
FD_ZERO(&rdset);
FD_SET(STDIN_FILENO, &rdset);
FD_SET(socketFd, &rdset);
ret = select(socketFd + 1, &rdset, NULL, NULL, NULL);
if(FD_ISSET(socketFd, &rdset)){
bzero(buf, sizeof(buf));
ret = recv(socketFd, buf, sizeof(buf), 0);
ERROR_CHECK(ret, -1, "recv");
if(ret == 0){
printf("byebye!\n");
break;
}
printf("%s\n", buf);
}
if(FD_ISSET(STDIN_FILENO, &rdset)){
memset(buf, 0, sizeof(buf));
ret = read(STDIN_FILENO, buf, sizeof(buf));
if(ret == 0){
printf("byebye!\n");
break;
}
ret = send(socketFd, buf ,strlen(buf) - 1, 0);
ERROR_CHECK(ret, -1, "send");
}
}
close(socketFd);
}
tcp_server.c
#include
int main(int argc,char* argv[])
{
ARGS_CHECK(argc,3);
int socketFd;
socketFd = socket(AF_INET,SOCK_STREAM,0);
ERROR_CHECK(socketFd, -1, "socket");
struct sockaddr_in ser;
bzero(&ser, sizeof(ser));
ser.sin_family = AF_INET;
ser.sin_port = htons(atoi(argv[2]));
ser.sin_addr.s_addr = inet_addr(argv[1]);//点分十进制转为32位的网络字节序
int ret;
ret = bind(socketFd, (struct sockaddr*)&ser, sizeof(ser));
ERROR_CHECK(ret, -1, "bind");
listen(socketFd, 10);//缓冲区的大小，一瞬间能够放入的客户端连接信息
int new_fd;
struct sockaddr_in client;
bzero(&client, sizeof(client));
int addrlen = sizeof(client);
new_fd = accept(socketFd, (struct sockaddr*)&client, &addrlen);
ERROR_CHECK(new_fd, -1, "accept");
printf("client ip=%s, port=%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
fd_set rdset;
char buf[128] = {0};
while(1){
FD_ZERO(&rdset);
FD_SET(STDIN_FILENO, &rdset);
FD_SET(new_fd, &rdset);
ret = select(new_fd + 1, &rdset, NULL, NULL, NULL);
if(FD_ISSET(new_fd, &rdset)){
bzero(buf, sizeof(buf));
ret = recv(new_fd, buf, sizeof(buf), 0);
ERROR_CHECK(ret, -1, "recv");
if(ret == 0){
printf("byebye!\n");
break;
}
printf("%s\n", buf);
}
if(FD_ISSET(STDIN_FILENO, &rdset)){
memset(buf, 0, sizeof(buf));
ret = read(STDIN_FILENO, buf, sizeof(buf));
if(ret == 0){
printf("byebye!\n");
break;
}
ret = send(new_fd, buf, strlen(buf) - 1, 0);
ERROR_CHECK(ret, -1, "send");
}
}
close(new_fd);
close(socketFd);
return 0;
}
2、TCP即时聊天升级：服务器在客户端断开后不断开，客户端可以多次重连服务器进行即时聊天
tcp_server.c
#include
int main(int argc,char* argv[])
{
ARGS_CHECK(argc,3);
int socketFd;
socketFd = socket(AF_INET,SOCK_STREAM,0);
ERROR_CHECK(socketFd, -1, "socket");
struct sockaddr_in ser;
bzero(&ser, sizeof(ser));
ser.sin_family = AF_INET;
ser.sin_port = htons(atoi(argv[2]));
ser.sin_addr.s_addr = inet_addr(argv[1]);//点分十进制转为32位的网络字节序
int ret;
ret = bind(socketFd, (struct sockaddr*)&ser, sizeof(ser));
ERROR_CHECK(ret, -1, "bind");
listen(socketFd, 10);//缓冲区的大小，一瞬间能够放入的客户端连接信息
int new_fd;
struct sockaddr_in client;
bzero(&client, sizeof(client));
int addrlen = sizeof(client);
char buf[128] = {0};
fd_set rdset;
fd_set needMonitorSet; //需要监听的描述符集合
FD_ZERO(&needMonitorSet);
FD_SET(STDIN_FILENO, &needMonitorSet);
FD_SET(socketFd, &needMonitorSet);
while(1){
memcpy(&rdset, &needMonitorSet, sizeof(fd_set));
ret = select(11, &rdset, NULL, NULL, NULL); //设最大监控描述符为10
if(FD_ISSET(socketFd, &rdset)){ //如果监听到客户端则accept接受远程计算机的连接请求
new_fd = accept(socketFd, (struct sockaddr*)&client, &addrlen); //accept函数接受一个连接时，会返回一个新的socket标识符，以后数据的数据传输和读取就要通过这个新的socket编号来处理，原来的socket继续监听其他客户机的连接请求。
ERROR_CHECK(new_fd, -1, "accept");
printf("client ip=%s, port=%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
FD_SET(new_fd, &needMonitorSet);
}
if(FD_ISSET(new_fd, &rdset)){
bzero(buf, sizeof(buf));
ret = recv(new_fd, buf, sizeof(buf), 0);
ERROR_CHECK(ret, -1, "recv");
if(ret == 0){
printf("byebye!\n");
FD_CLR(new_fd, &needMonitorSet); //从needMonitorSet中删除new_fd
close(new_fd);
continue;
}
printf("%s\n", buf);
}
if(FD_ISSET(STDIN_FILENO, &rdset)){
memset(buf, 0, sizeof(buf));
ret = read(STDIN_FILENO, buf, sizeof(buf));
if(ret == 0){
printf("byebye!\n");
break;
}
ret = send(new_fd, buf, strlen(buf) - 1, 0);
ERROR_CHECK(ret, -1, "send");
}
}
close(socketFd);
return 0;
}
tcp_client.c和1同
3、使用UDP协议的流程图
服务端：socket---bind---recvfrom---sendto---close
客户端：socket----------sendto---recvfrom---close
sendto()函数原型：
int sendto(int sockfd, const void msg,int len,unsigned int flags,const struct sockaddrto, int tolen);
该函数比send()函数多了两个参数，to表示目地机的IP地址和端口号信息，而tolen常常被赋值为sizeof (struct sockaddr)。sendto 函数也返回实际发送的数据字节长度或在出现发送错误时返回-1。
recvfrom()函数原型：
**int recvfrom(int sockfd,void buf,int len,unsigned int flags,struct sockaddrfrom,int *fromlen);**
from是一个struct sockaddr类型的变量，该变量保存连接机的IP地址及端口号。fromlen常置为sizeof (struct sockaddr)。当recvfrom()返回时，fromlen包含实际存入from中的数据字节数。Recvfrom()函数返回接收到的字节数或当出现错误时返回-1，并置相应的errno。
UDP传输一个数据报示例：
udp_server.c
#include
int main(int argc, char **argv){
ARGS_CHECK(argc, 3);
int socketFd;
socketFd = socket(AF_INET, SOCK_DGRAM, 0);
ERROR_CHECK(socketFd, -1, "socket");
struct sockaddr_in ser;
bzero(&ser,sizeof(ser));
ser.sin_family = AF_INET;
ser.sin_port = htons(atoi(argv[2]));
ser.sin_addr.s_addr = inet_addr(argv[1]);//点分十进制转为32位的网络字节序
int ret;
ret = bind(socketFd, (struct sockaddr*)&ser, sizeof(ser));
ERROR_CHECK(ret, -1, "bind");
char buf[128] = {0};
struct sockaddr_in client;
int addrlen = sizeof(client);
ret = recvfrom(socketFd, buf, 5, 0, (struct sockaddr*)&client, &addrlen);
ERROR_CHECK(ret, -1, "recvfrom");
printf("client ip = %s, port = %d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
printf("udp server gets %s\n", buf);
//bzero(buf, sizeof(buf));
//ret = recvfrom(socketFd, buf, 5, 0, (struct sockaddr*)&client, &addrlen);
//ERROR_CHECK(ret, -1, "recvfrom");
//printf("udp server gets %s\n", buf);
ret = sendto(socketFd, "world", 5, 0, (struct sockaddr*)&client, sizeof(client));
ERROR_CHECK(ret, -1, "sendto");
close(socketFd);
return 0;
}
udp_client.c
#include
int main(int argc, char *argv[]){
ARGS_CHECK(argc, 3);
int socketFd;
socketFd = socket(AF_INET, SOCK_DGRAM, 0);
ERROR_CHECK(socketFd, -1, "socket");
struct sockaddr_in ser;
bzero(&ser, sizeof(ser));
ser.sin_family = AF_INET;
ser.sin_port = htons(atoi(argv[2]));
ser.sin_addr.s_addr = inet_addr(argv[1]);
int ret;
ret = sendto(socketFd, "helloworld", 10, 0, (struct sockaddr*)&ser, sizeof(ser));
ERROR_CHECK(ret, -1, "sendto");
char buf[128] = {0};
ret = recvfrom(socketFd, buf, sizeof(buf), 0, NULL, NULL);
ERROR_CHECK(ret, -1, "recvfrom");
printf("udp client gets %s\n", buf);
close(socketFd);
return 0;
}
4、使用UDP协议建立即时连接
udp_server.c
#include
int main(int argc, char **argv){
ARGS_CHECK(argc, 3);
int socketFd;
socketFd = socket(AF_INET, SOCK_DGRAM, 0);
ERROR_CHECK(socketFd, -1, "socket");
struct sockaddr_in ser;
bzero(&ser,sizeof(ser));
ser.sin_family = AF_INET;
ser.sin_port = htons(atoi(argv[2]));
ser.sin_addr.s_addr = inet_addr(argv[1]);//点分十进制转为32位的网络字节序
int ret;
ret = bind(socketFd, (struct sockaddr*)&ser, sizeof(ser));
ERROR_CHECK(ret, -1, "bind");
char buf[128] = {0};
struct sockaddr_in client;
int addrlen = sizeof(client);
printf("client ip = %s, port = %d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
fd_set rdset;
while(1){
FD_ZERO(&rdset);
FD_SET(STDIN_FILENO, &rdset);
FD_SET(socketFd, &rdset);
ret = select(socketFd + 1, &rdset, NULL, NULL, NULL);
if(FD_ISSET(socketFd, &rdset)){
bzero(buf, sizeof(buf));
ret = recvfrom(socketFd, buf, sizeof(buf), 0, (struct sockaddr*)&client, &addrlen);
ERROR_CHECK(ret, -1, "recvfrom");
printf("%s\n", buf);
}
if(FD_ISSET(STDIN_FILENO, &rdset)){
bzero(buf, sizeof(buf));
ret = read(STDIN_FILENO, buf, sizeof(buf));
if(0 == ret){
printf("byeybye\n");
break;
}
ret = sendto(socketFd, buf, strlen(buf) - 1, 0, (struct sockaddr*)&client, sizeof(client));
ERROR_CHECK(ret, -1, "sendto");
}
}
close(socketFd);
return 0;
}
udp_client.c
#include
int main(int argc, char *argv[]){
ARGS_CHECK(argc, 3);
int socketFd;
socketFd = socket(AF_INET, SOCK_DGRAM, 0);
ERROR_CHECK(socketFd, -1, "socket");
struct sockaddr_in ser;
bzero(&ser, sizeof(ser));
ser.sin_family = AF_INET;
ser.sin_port = htons(atoi(argv[2]));
ser.sin_addr.s_addr = inet_addr(argv[1]);
int ret;
char buf[128] = {0};
fd_set rdset;
while(1){
FD_ZERO(&rdset);
FD_SET(STDIN_FILENO, &rdset);
FD_SET(socketFd, &rdset);
ret = select(socketFd + 1, &rdset, NULL, NULL, NULL);
if(FD_ISSET(socketFd, &rdset)){
bzero(buf, sizeof(buf));
ret = recvfrom(socketFd, buf, sizeof(buf), 0, NULL, NULL);
ERROR_CHECK(ret, -1, "recvfrom");
printf("%s\n", buf);
}
if(FD_ISSET(STDIN_FILENO, &rdset)){
bzero(buf, sizeof(buf));
ret = read(STDIN_FILENO, buf, sizeof(buf));
if(0 == ret){
printf("byeybye\n");
break;
}
ret = sendto(socketFd, buf, strlen(buf) - 1, 0, (struct sockaddr*)&ser, sizeof(ser));
ERROR_CHECK(ret, -1, "sendto");
}
}
close(socketFd);
return 0;
}
5、如果在已经处于 ESTABLISHED状态下的socket(一般由端口号和标志符区分)需调用closesocket(一般不会立即关闭而经历TIME_WAIT的过程)后想继续重用该socket，但也可以直接用setsockopt和reuse。
int reuse=1;
setsockopt(s,SOL_SOCKET ,SO_REUSEADDR,(const char*)&reuse,sizeof(int));
tcp_server.c
#include
int main(int argc,char* argv[])
{
ARGS_CHECK(argc,3);
int socketFd;
socketFd = socket(AF_INET,SOCK_STREAM,0);
ERROR_CHECK(socketFd, -1, "socket");
int ret;
int reuse = 1;
ret = setsockopt(socketFd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(int));
ERROR_CHECK(ret, -1, "setsockopt");
struct sockaddr_in ser;
bzero(&ser, sizeof(ser));
ser.sin_family = AF_INET;
ser.sin_port = htons(atoi(argv[2]));
ser.sin_addr.s_addr = inet_addr(argv[1]);//点分十进制转为32位的网络字节序
ret = bind(socketFd, (struct sockaddr*)&ser, sizeof(ser));
ERROR_CHECK(ret, -1, "bind");
listen(socketFd, 10);//缓冲区的大小，一瞬间能够放入的客户端连接信息
int new_fd;
struct sockaddr_in client;
bzero(&client, sizeof(client));
int addrlen = sizeof(client);
new_fd = accept(socketFd, (struct sockaddr*)&client, &addrlen);
ERROR_CHECK(new_fd, -1, "accept");
printf("client ip=%s, port=%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
fd_set rdset;
char buf[128] = {0};
while(1){
FD_ZERO(&rdset);
FD_SET(STDIN_FILENO, &rdset);
FD_SET(new_fd, &rdset);
ret = select(new_fd + 1, &rdset, NULL, NULL, NULL);
if(FD_ISSET(new_fd, &rdset)){
bzero(buf, sizeof(buf));
ret = recv(new_fd, buf, sizeof(buf), 0);
ERROR_CHECK(ret, -1, "recv");
if(ret == 0){
printf("byebye!\n");
break;
}
printf("%s\n", buf);
}
if(FD_ISSET(STDIN_FILENO, &rdset)){
memset(buf, 0, sizeof(buf));
ret = read(STDIN_FILENO, buf, sizeof(buf));
if(ret == 0){
printf("byebye!\n");
break;
}
ret = send(new_fd, buf, strlen(buf) - 1, 0);
ERROR_CHECK(ret, -1, "send");
}
}
close(new_fd);
close(socketFd);
return 0;
}
tcp_client.c和1同
6、SO_RCVLOWAT：接收缓冲区下限
tcp_server_rcvlowat.c
#include
int main(int argc,char* argv[])
{
ARGS_CHECK(argc,3);
int socketFd;
socketFd = socket(AF_INET,SOCK_STREAM,0);
ERROR_CHECK(socketFd, -1, "socket");
int ret;
int reuse = 1;
ret = setsockopt(socketFd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(int));
ERROR_CHECK(ret, -1, "setsockopt");
struct sockaddr_in ser;
bzero(&ser, sizeof(ser));
ser.sin_family = AF_INET;
ser.sin_port = htons(atoi(argv[2]));
ser.sin_addr.s_addr = inet_addr(argv[1]);//点分十进制转为32位的网络字节序
ret = bind(socketFd, (struct sockaddr*)&ser, sizeof(ser));
ERROR_CHECK(ret, -1, "bind");
listen(socketFd, 10);//缓冲区的大小，一瞬间能够放入的客户端连接信息
int new_fd;
struct sockaddr_in client;
bzero(&client, sizeof(client));
int addrlen = sizeof(client);
new_fd = accept(socketFd, (struct sockaddr*)&client, &addrlen);
ERROR_CHECK(new_fd, -1, "accept");
printf("client ip=%s, port=%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
fd_set rdset;
char buf[128] = {0};
int rcvLowAt = 10;
ret=setsockopt(new_fd,SOL_SOCKET,SO_RCVLOWAT,&rcvLowAt,sizeof(int));
ERROR_CHECK(ret, -1, "setsockopt");
while(1){
FD_ZERO(&rdset);
FD_SET(STDIN_FILENO, &rdset);
FD_SET(new_fd, &rdset);
ret = select(new_fd + 1, &rdset, NULL, NULL, NULL);
if(FD_ISSET(new_fd, &rdset)){
bzero(buf, sizeof(buf));
ret = recv(new_fd, buf, sizeof(buf), 0);
ERROR_CHECK(ret, -1, "recv");
if(ret == 0){
printf("byebye!\n");
break;
}
printf("%s\n", buf);
}
if(FD_ISSET(STDIN_FILENO, &rdset)){
memset(buf, 0, sizeof(buf));
ret = read(STDIN_FILENO, buf, sizeof(buf));
if(ret == 0){
printf("byebye!\n");
break;
}
ret = send(new_fd, buf, strlen(buf) - 1, 0);
ERROR_CHECK(ret, -1, "send");
}
}
close(new_fd);
close(socketFd);
return 0;
}
tcp_client.c和1同